Add Databases Course in free-courses-en.md (Changes made) (#11452)

* Add HTML Course

* Add FreeCodeCamp AI Course in free-courses-en.md

* Add Databases Course in free-courses-en.md

* Update courses/free-courses-en.md

Co-authored-by: Eric Hellman <eric@hellman.net>

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Co-authored-by: Eric Hellman <eric@hellman.net>

courses/free-courses-en.md

@@ -565,6 +565,7 @@
 * [Database Management Systems](https://www.youtube.com/playlist?list=PLBlnK6fEyqRi_CUQ-FXxgzKQ1dwr_ZJWZ) - Neso Academy
 * [Database Systems](http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-830-database-systems-fall-2010/) (MIT's opencourseware)
 * [Database Systems - Cornell University Course (SQL, NoSQL, Large-Scale Data Analysis)](https://www.youtube.com/watch?v=4cWkVbC2bNE) - Professor Immanuel Trummer, freeCodeCamp.org
+* [Databases in Depth](https://www.youtube.com/playlist?list=PLliXPok7ZonnALnedG5doBOSCXlU14yJF) - Keerti Purswani
 * [DBMS for GATE Exams](https://www.youtube.com/playlist?list=PLWPirh4EWFpGrpcMfZ6UcdI786QdtSxV8) - Tutorialspoint
 * [DBMS Placement Series](https://www.youtube.com/playlist?list=PLDzeHZWIZsTpukecmA2p5rhHM14bl2dHU) - CodeHelp by Babbar
 * [DML Server Administration](https://alison.com/course/databases-dml-statements-and-sql-server-administration-revised) (Alison)