Revise maintenance status and contribution guidelines

CONTRIBUTING.md

@@ -2,18 +2,30 @@
 
 **Please read the following text before creating a pull request.**
 
-This project is organized and supported by contributions from the community. Maintenance is done in our limited time.
-We welcome any pull request that contributes to PDFParser (code, documentation, ...).
-However, we would like to point out that you are initially responsible for a contribution.
-If you are new to dealing with pull requests, you can find more information at [Github documentation](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/about-pull-requests).
+This project is maintained by the community in very limited time.
+**At this point, contributions are effectively limited to:**
+- small, well-scoped bug fixes
+- PHP compatibility updates
+- documentation improvements
+- related tests
+
+**Do not** open pull requests for new features, larger refactorings, deep parser changes, performance projects, or broader behavior changes.
+Such contributions are unlikely to be reviewed, merged, or maintained responsibly in the current state of the project.
+
+If you are unsure whether a change is small enough in scope, please open an [issue](https://github.com/smalot/pdfparser/issues) first and ask before investing significant time.
+
+If you are new to pull requests, you can find more information in the [GitHub documentation](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/about-pull-requests).
+
 Please don't just throw code at us and expect us to handle it.
-Nevertheless, we will support you and give you feedback.
+We will try to give feedback where possible, but contributor support is also limited by time and available project knowledge.
+
+## CI
 
 To make life easier for you and us, there is a Continuous Integration (CI) system that carries out software tests and performs a number of other tasks.
 The following points describe the relevant preparations/inputs for the CI system.
 All checks must be green, otherwise a pull request will not be accepted.
-* Please create an [issue](https://github.com/smalot/pdfparser/issues) before starting work on any significant changes.
-* We only accept code that is bundled with tests, regardless of whether it is a new function or a bug fix. This strengthens the code base and avoids later regressions. :exclamation: **If you don't know how to write a test, tell us upfront when you open the pull request and we might add them ourselves or discuss other ways**. This [Medium article](https://pguso.medium.com/a-beginners-guide-to-phpunit-writing-and-running-unit-tests-in-php-d0b23b96749f) might be a good starting point. Code changes without tests are very likely to be rejected.
+* If your change goes beyond a small, well-scoped bug fix, please open an [issue](https://github.com/smalot/pdfparser/issues) first to clarify whether it is within the current maintenance scope of this project.
+* We only accept code that is bundled with tests. This applies to bug fixes as well as compatibility-related changes. This strengthens the code base and avoids later regressions. :exclamation: **If you don't know how to write a test, tell us upfront when you open the pull request and we might add them ourselves or discuss other ways**. This [Medium article](https://pguso.medium.com/a-beginners-guide-to-phpunit-writing-and-running-unit-tests-in-php-d0b23b96749f) might be a good starting point. Code changes without tests are very likely to be rejected.
 * Fix reported issues with the coding style. We use **PHP-CS-Fixer** for this. See [.php-cs-fixer.php](./.php-cs-fixer.php) for more information about our coding styles. [Developer.md](./doc/Developer.md) contains more information about this topic.
 * If you are fixing an **existing error**, refer to it in the introduction text of the pull request. For example, if you created a fix for issue `#1234` write the following Markdown: `fixes #1234`.
-* In case you have changed **internal behavior/functionality**, check our documentation to make sure these changes are **correctly documented**: https://github.com/smalot/pdfparser/tree/master/doc
+* If your bug fix or compatibility change affects documented behavior, please update the documentation accordingly: https://github.com/smalot/pdfparser/tree/master/doc

README.md

@@ -8,9 +8,11 @@
 
 The `smalot/pdfparser` is a standalone PHP package that provides various tools to extract data from PDF files.
 
-This library is under **active maintenance**.
-There is no active development by the author of this library (at the moment), but we welcome any pull request adding/extending functionality!
-See [CONTRIBUTING.md](./CONTRIBUTING.md) for further information about how to contribute.
+### Maintenance status
+
+This library is under **limited maintenance**.
+It is still kept compatible with supported PHP versions, and community contributions may be accepted. However, there is currently **no active feature development** and **no guarantee** that pull requests will be reviewed or merged in a timely manner. 
+If you plan to contribute anything beyond a small, well-scoped fix, please read [CONTRIBUTING.md](./CONTRIBUTING.md) first.
 
 ## Features