Deprecate built-in FTL Extractor

[andrew000]

Why deprecate built-in FTL Extractor?

• Has many bugs, such as #32 and #33
• Is not maintained
• Uses regex for parsing .ftl
• Uses large libcst instead of built-in ast to search in-code ftl-keys

I recommend using FTL-Extract library by @andrew000

• PyPI
• GITHUB

👍 It uses fluent.syntax to work with .ftl and built-in python library ast.