Topic/going public

[Espen Hovland (eshovlan)]

Paperwork attempt 2, Electric boogaloo

[cursor]

PR Summary

Low Risk
Documentation and CI trigger changes only; deleted ruleset files are not applied by the workflow YAML and branch protection would be configured in GitHub org/repo settings separately.

Overview
Prepares GitHub metadata for open-source use by tailoring contributor guidance and CI automation to this repository instead of generic Silicon Labs firmware templates.

CONTRIBUTING.md fixes minor wording and replaces the old workflow checklist (coding convention, firmware Docker build, TruffleHog) with a single link to unittest-and-coverage.yml, noting coverage should stay in the high 90s.

unittest-and-coverage.yml now runs on push and pull_request targeting main and develop/**, in addition to manual workflow_dispatch.

Removes .github/rulesets/Silabs-basic-public-ruleset.json and Silabs-basic-ruleset-internal.json—exported rulesets that still referenced other template repos (devs-template-public / devs-template) rather than this project.

^{Reviewed by Cursor Bugbot for commit cd59b43. Bugbot is set up for automated code reviews on this repo. Configure here.}