Add issue and pull request templates (fixes #447)

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,35 @@
+---
+name: Bug report
+about: Report a problem or unexpected behavior in nidm-specs
+labels: bug
+---
+
+**Describe the bug**
+
+A clear and concise description of what the bug is.
+
+**To Reproduce**
+
+Steps to reproduce the behavior:
+
+1. …
+2. …
+3. …
+
+**Expected behavior**
+
+A clear and concise description of what you expected to happen.
+
+**Screenshots / logs**
+
+If applicable, add screenshots or relevant log/output.
+
+**Environment**
+
+- OS:
+- Python version (if relevant):
+- nidm-specs version / commit:
+
+**Additional context**
+
+Add any other context about the problem here.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,21 @@
+---
+name: Feature request
+about: Suggest an enhancement or new specification for nidm-specs
+labels: enhancement
+---
+
+**Is your feature request related to a problem? Please describe.**
+
+A clear and concise description of what the problem is.
+
+**Describe the solution you’d like**
+
+A clear and concise description of what you want to happen.
+
+**Describe alternatives you’ve considered**
+
+A clear and concise description of any alternative solutions or features.
+
+**Additional context**
+
+Add any other context, examples, or references here.

.github/pull_request_template.md

@@ -0,0 +1,18 @@
+## Summary
+
+Briefly describe the changes in this pull request.
+
+## Related issue
+
+Link to the issue(s) this PR addresses, e.g. `Fixes #447`.
+
+## Changes proposed
+
+- …
+
+## Checklist
+
+- [ ] I followed the CONTRIBUTING guidelines for this project.
+- [ ] I updated documentation where necessary.
+- [ ] I ran existing tests (if applicable) and they pass.
+- [ ] I described the change clearly in this PR.