library: Add Language and Category filters

[BharatAtbrat]

Initial implementation to add language and category filters for available demos. Minor issue

• ~~With the current implementation the Dropdown uses a StringList to store the names of the categories, and Platform APIs as a category only shows demos if the category is named Platform in the string list. Therefore the category in the dropdown is also shown as Platform instead of the ideal Platform APIs~~
• Another thing I noticed is when the scroll is at the topmost position (default) it takes two clicks to select the overflowing demo categories. Screengrab of it in action:

https://github.com/user-attachments/assets/08eab5cb-3533-457a-b3e7-a4bb5b3d6edb

Let me know if there are any issues with the implementation :)

Current state [commit]

https://github.com/user-attachments/assets/4dd3d5e1-267f-4506-b4f0-32b34acd5146