[ENHANCEMENT] Add web features YAML link

**Is your feature request related to a problem? Please describe.**

I'd like to see the YAML definition of the web feature to know example what MDN BCD properties are included in this feature. Currently I have to look this up manually.

**Describe the solution you'd like**

A link, similar to the WPT.FYI link in the top right linking directly to the YAML definition in the Web DX Features github repo.

**Describe alternatives you've considered**

Manually navigation to the Web DX Features github repo.

**Additional context**

None

Start by locating the existing WPT.FYI link in the feature detail page and inspect how its destination is constructed. Use the Web DX Features GitHub repository as the reference for the YAML destination; done means the page exposes a neighboring link that opens the current feature's YAML definition.

Written by the indexing model from the issue text.