🐛 [Bug-Fix] Fix all inaccessible links in docs

[Skyenought]

Description

There were some links in readme that didn't work due to a refactoring of the official fiber website, so I fixed them.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• For new functionalities I follow the inspiration of the express js framework and built them similar in usage
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation - /docs/ directory for https://docs.gofiber.io/
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• If new dependencies exist, I have checked that they are really necessary and agreed with the maintainers/community (we want to have as few dependencies as possible)
• I tried to make my code as fast as possible with as few allocations as possible
• For new code I have written benchmarks so that they can be analyzed and improved

Commit formatting:

Use emojis on commit messages so it provides an easy way of identifying the purpose or intention of a commit. Check out the emoji cheatsheet here: https://gitmoji.carloscuesta.me/

[ReneWerner87]

thx
i also added some fallbacks for old versions
https://github.com/gofiber/docs/blob/master/docusaurus.config.js#L34-L36