Documentation work; added platform-specific notes for nix

[pelasgus]

…v env via nix for rust dev.

What kind of change does this PR introduce?

• Bugfix
• Feature
• Docs
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change?

• Yes
• No

Checklist

• This PR will resolve #___
• A change file is added if any packages will require a version bump due to this PR per the instructions in the readme.
• I have added a convincing reason for adding this feature, if necessary
• It can be built on all targets and pass CI/CD.

Other information

[pelasgus]

Implemented all requested changes; pending approval.

[amrbashir]

Oh looks like you didn't sign your first commit and I can't merge the PR unless all commits are signed. You need to setup commit signing, then you can sign past commit like this for example.

[pelasgus]

@amrbashir just merge this anyway, your commits cannot be fully verified, its you and my original commit that are blocking merge. Please rectify, cheers

[amrbashir]

Partially verified commits are fine, but you have one commit at the beginning of the PR that is not verified.

You can try squashing all commits into one verified commit or close this PR and re-open a new one.

Otherwise our guidelines and repo configuration prevents anyone from bypassing this requirement.