docs: polish readme, update example.env, and gitignore

[nicokempe]

What kind of change does this PR introduce?

Docs update / configuration cleanup

What is the current behavior?

• README contained inconsistent wording, capitalization, and formatting.
• example.env provider sections weren’t fully normalized (e.g., brand naming).
• .idea IDE files were not ignored, risking accidental commits.

What is the new behavior?

• README polished for clarity and consistency (terminology, grammar, branding).
• example.env updated with cleaner provider sections and improved comments (e.g., explicit Twitter (X) naming).
• .gitignore updated to exclude .idea directories.
• Inherited features section: updated the outdated note on JWT signing. It now reflects current Supabase Auth behavior: asymmetric signing keys (RS256 by default, ECC/Ed25519 optional) are supported and recommended, while HS256 remains for compatibility.

Additional context

This PR improves documentation and developer ergonomics only. Read through the readme because I wanted to contribute to the project and just updated everything that didn't look right. No functional or runtime changes.

[cstockton]

Thanks!

[coveralls]

Pull Request Test Coverage Report for Build 18412227177

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 67.568%

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Totals
Change from base Build 18323958405:	0.0%
Covered Lines:	13438
Relevant Lines:	19888

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💛 - Coveralls

[uyarburak]

Hi @cstockton, Could you confirm if this line is true:

auth/README.md

Line 1135 in 21f3070

If `"create_user": true`, user will not be automatically signed up if the user doesn't exist.

[cstockton]

@uyarburak Good catch, you may make a separate PR for that if you would like.