Add support for showing multiple Linear issues if found

[delucis]

Currently we show the most recently created Linear issue in the sidebar on GitHub. Linear and GH issues are not 1<>1 — you can have multiple Linear issues for a single GH issue potentially.

It would be good to support expanding the Linear section of the sidebar to show additional issues if found.

Default view could be something like this:

And expand to multiple cards when clicked.

Other ideas:

• Sidebar ticket ordering #12
• Indicate the status of additional issues in the “more issues” link, e.g. using Linear’s progress icons

[sarah11918]

Great issue, Chris!