Update contributing notes and PR template

See https://github.com/Jermolene/TiddlyWiki5/pull/6511#issuecomment-1080430636

.github/PULL_REQUEST_TEMPLATE/pull_request_template.md

@@ -20,3 +20,11 @@ A clear and concise description of any alternative solutions or features you've
 Add any other context or screenshots about the feature request here.
 
 If you link to discussions elsewhere then please copy and paste the important text, and don't expect readers to scan the entire discussion to find the relevant part.
+
+## Checklist before requesting a review
+
+- [ ] Illustrate any visual changes (however minor) with before/after screenshots
+- [ ] Self-review of code
+- [ ] Documentation updates (for user-visible changes)
+- [ ] Tests (for core code changes)
+- [ ] Complies with coding style guidelines (for JavaScript code)

editions/tw5.com/tiddlers/community/Contributing.tid

@@ -1,5 +1,5 @@
 created: 20131101111400000
-modified: 20211115092001000
+modified: 20220328105410721
 tags: Community
 title: Contributing
 type: text/vnd.tiddlywiki
@@ -20,6 +20,7 @@ PRs must meet these minimum requirements before they can be considered for mergi
 * The title of the PR should be written in the imperative mood. See below
 * Adequate explanation in the body of the PR for the motivation and implementation of the change. Focus on the //why// and //what//, rather than the //how//
 * PRs must be self-contained. Although they can link to material elsewhere, everything needed to understand the intention of the PR should be included
+* Any visual changes introuced by the PR should be noted and illustrated with before/after screenshots
 * Documentation as appropriate for end-users or developers
 * Observe the coding style
 * Read the developers documentation