Fix filename typo, Fix Returns Comment

[lorenzolewis]

• Rename a file from readm3.ts to readme.ts
• Fix a regression where the comments in a return block weren't rendered (reference Embed all objects under a Module/Namespace onto single page #338 (comment))

[lorenzolewis]

Also added in a fix for some links. If you're wanting to use <a href="..." /> syntax then you'll need to strip the .md extension from the files (current the context.urlTo() function isn't doing that). If you leave the extension then it's a broken link.

[lorenzolewis]

Closing in favour of #347, #348, and #349 (and to close the PR from our main next branch)