Update README.md

Author: banerjeesamrat

README.md

@@ -25,7 +25,7 @@
 * [x] Chapter 4 – Lists
 * [x] Chapter 5 – Dictionaries and Structuring Data
 * [x] Chapter 6 – Manipulating Strings
-* [ ] Chapter 7 – Pattern Matching with Regular Expressions
+* [x] Chapter 7 – Pattern Matching with Regular Expressions
 * [ ] Chapter 8 – Reading and Writing Files
 * [ ] Chapter 9 – Organizing Files
 * [ ] Chapter 10 – Debugging