Adding lesson 7 to readme

Author: Cheukting

getting_started/python-client/README.md

@@ -8,6 +8,7 @@ This is a step by step tutorial to get you started using TerminusDB/ TerminusX f
 - [Lesson 4 - Update and import new data that links to old data](lesson_4.md)
 - [Lesson 5 - Query on the database and get result back as CSV or DataFrame](lesson_5.md)
 - [Lesson 6 - Version control: time travel, branching and rebase](lesson_6.md)
+- [Lesson 7 - Logical query using triple and WOQL](lesson_7.md)
 
 ## Extra lessons: