fix: Revise length of generated GitHub issue link to avoid hitting URI max length

[stalgiag]

This PR truncates conflict markdown when a "Raise an issue" link has more than 8k chars.

Assumptions:

• 8k was tested in Chrome, Firefox, and Safari. It works on all. There is conflicting information about the limits for Edge but the most up-to-date info suggests that it shares Chrome's limit which would make sense.
• I couldn't create a testing scenario in which anything other than conflict markdown creates an issue link that exceeds this limit. If a reviewer believes otherwise please let me know.

This PR isn't entirely satisfying as it does result in truncated data in the issue. I tried to mitigate the worst effects of this by including a link back to the originating location. I looked into other options but the tradeoffs didn't seem worth it.

Alternatives

• Creating a GH issue via post to GH API
  • pros: no limitation on content
  • cons: would come from a central account rather than users' personals
• Replacing body with a link to a central view of the relevant info in the app
  • pros: no limitations on content, freedom with presentation
  • cons: requires navigating away from GH

related to #1334