Extend automatic rendered link to the blog.rust-lang.org repo

[Urgau]

This PR extends the automatic addition of the "Rendered" link to the blog.rust-lang.org repo, as is currently done for the rfcs repo.

[apiraino]

Maybe it's me but I don't understand what this patch is doing (I feel it's doing something useful). Can you please provide an example? 🙂

[Urgau]

Sure, currently when opening a PR on the rust-lang/rfcs repo, triagebot will append to the PR description a link to directly see the rendered RFC without having to manually add it (for PR author) and manually find it (by looking at the modified files and clicking on view file).

An example can be found on rust-lang/rfcs#3683 (comment), where it can be seen that rustbot/triagebot modified the PR description to add that rendered link. Such example can be found on all RFCs PR.

This PR just modifies the triggering logic to also apply this useful logic to the blog repo.

[apiraino]

Ah OK, so the blog posts PRs will automatically have the markdown rendered link in the opening comment instead of the user having to click around and find it themself.

Cool, thanks.

[ehuss]

Thanks! I'm a little on the fence with how useful this is. There are also some drawbacks (like these links will often be broken after merging). However, I don't think it should cause too much harm, and we can easily revert this if people have problems with it.