This PR adds `golangci-lint` based on the configuration from
`coder/coder`
([here](https://github.com/coder/coder/blob/main/.golangci.yaml)) then
migrated to v2 using `golangci-lint migrate` plus the addition of few
more linters.
---------
Signed-off-by: Callum Styan <callumstyan@gmail.com>
Closes https://github.com/coder/internal/issues/531
## Changes made
- Added functionality to validate the structure of module README files (frontmatter and the README body)
- Added a really basic snapshot-ish test for the module README body validation
- Updated README files that were previously violating README requirements (the old modules validation logic wasn't catching these)
- Changed `ValidationPhase` from an int to a string
