Migrate to Manifest V3; modernize build (fixes #33)

[JoshuaKimsey]

Summary

Migrates The Printliminator from Manifest V2 to V3 so it loads in modern Chrome again. The current Web Store listing installs a broken extension.

See #33 for the full context.

Changes

Manifest V3 (src/chrome/manifest.json)

• manifest_version 2 → 3; version 4.0.5 → 5.0.0
• browser_action → action
• Added scripting permission
• web_accessible_resources: string array → object form with matches: ["<all_urls>"]

API migration (src/chrome/popup.js)

• chrome.tabs.executeScript → chrome.scripting.executeScript
• chrome.tabs.insertCSS → chrome.scripting.insertCSS
• code: string injection → func: arrow functions
• file: → files: arrays
• Result reads updated from result[0] → result[0].result (affects the print ready-state polling loop)
• Implicit active-tab targeting (null tabId) → explicit target: { tabId } from the already-queried tabArray[0].id
• matchAboutBlank dropped (no MV3 equivalent — Yahoo Mail print-popup edge case deferred; documented in the README)

Build modernization

• Replaced the 2015 Grunt 0.4 + grunt-preprocess pipeline with a zero-dependency build.js (Node)
• Single dev dependency: sass (Dart Sass ^1.77.0) for SCSS compilation
• npm run build / npm run clean scripts; outputs dist/chrome/
• Replicates the original @echo / @if MODE / {version} preprocessing semantics exactly
• Chrome extension output only; bookmarklet build path untouched (unaffected by MV3)

Other

• README: added v5.0.0 changelog entry, building-from-source section, fork notice
• Manifest contributors field added crediting original authors + MV3 migration
• homepage_url pointed to the active fork
• Build now includes all 5 locales (de, en, fr, pt_BR, sr); previous committed dist/ only shipped en and fr

Verification

• npm run build produces a loadable dist/chrome/ (14 files + 5 locale folders)
• Manifest validated as MV3 JSON
• No leftover chrome.tabs.executeScript/insertCSS calls in output
• No unprocessed @echo/@if/{version} directives in output
• printliminator.js diff vs old committed dist: only the version string changed
• popup.html diff vs old committed dist: byte-identical
• Tested in Chrome: loads as unpacked extension, all four popup buttons (Undo, Stylize, Remove Graphics, Print) work, keyboard commands work (arrows, Enter, Backspace, +/-, Esc, Alt+click, Shift+click). Functionally identical to v4.0.5.

Notes

• I'm also publishing this as a separate Web Store listing under my account, since the original listing is under CSS-Tricks' account and this PR may not be reviewed. If this PR is merged, I'm happy to coordinate on the Web Store listing (e.g., transfer ownership or redirect users).
• The matchAboutBlank edge case (Yahoo Mail print popups) is deferred — documented in the README limitations section. Core functionality on normal pages is unaffected.
• Tagged as v5.0.0 on my fork.