Set up project scaffolding: GitHub Actions workflows, issue templates, changelog, contributing guidelines, MIT license, and README

.github/PULL_REQUEST_TEMPLATE.md

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+## Description
+
+<!-- Briefly: what does this PR do? -->
+
+## Type of change
+
+- [ ] Bug fix
+- [ ] New feature
+- [ ] Refactoring / docs
+- [ ] Other
+
+## Checklist
+
+- [ ] `./gradlew build` passes locally
+- [ ] Relevant tests updated or added (if applicable)