Support for env files

[haidubogdan]

This pull request proposes support for .env files.
Maybe it has too much features for the daily usage for these kind of files, but I think it's something to be discussed.
As the feedback progresses I can add more unit tests.

Implementations :

• mime provider for .env files
• coloring support

• coloring options for keyword like values (null, true, false ...)
• interpolated env key features like completion and declaration finder
• partial ticket fix Add comment/uncomment options on .properties, .cnf, .env files #6677 covering env files
• hints for duplicate key assignment
• important file node inclusion for .env file for web and php projects

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