Add a link to the policy file from the detail UI

[bluekeyes]

The repository badge in the upper left corner now includes the target
branch name and is a link to the policy file.

Note that this does not resolve references: it always links to the policy.yml in your repository, not the one that defines the actual rules. While resolving references shows the actual policy definition, it may not be obvious that the current repository uses a reference if we link directly to the referenced file.

Here's a preview of the new button:

[jmcampanini]

nice!

nit: i know that the button is clickable since i read this. i wonder if there's a way to make it more apparent, like an icon, or something? not sure what that would be though

[bluekeyes]

When you hover over it, the text and background change color and the cursor icon switches to a pointer. Do you think that's enough? There's also title text that appears that says "View policy definition on GitHub".

I could also look at changing the colors to be blue or have an underline to make it more link-y.

[jmcampanini]

pretty sure im just over-optimizing, as is should be good

[asvoboda]

👍 snazzy