Contributing to the documentation only requires a GitHub account. You can use the Edit on GitHub button in the top-right corner of any documentation page (except the class reference, as it's generated from a different repository):
No programming knowledge is required. reStructuredSyntax is used for markup, which has many differences from Markdown. For quick edits, you probably just need to copy existing markup, so you don't need to learn it specifically.
You can also report documentation issues on GitHub, but opening a pull request is the best way to contribute.