CI: Switch to using GitHub Actions

This change switches the CI setup for the repo away from Travis and over
to GitHub Actions, using https://github.com/w3c/spec-prod

It also renames the spec source file to index.bs, to follow Bikeshed
naming conventions, and it removes the generated output file
(index.html) from version control in the repo.

.github/workflows/build-validate-publish.yml

@@ -0,0 +1,20 @@
+name: CI
+on:
+  pull_request: {}
+  push:
+    branches: [main]
+
+jobs:
+  main:
+    name: Build, Validate, and Publish
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v2
+      - uses: w3c/spec-prod@v2
+        with:
+          GH_PAGES_BRANCH: gh-pages
+          BUILD_FAIL_ON: nothing
+          VALIDATE_LINKS: false
+          VALIDATE_MARKUP: true
+          W3C_ECHIDNA_TOKEN: ${{ secrets.ECHIDNA_TOKEN }}
+          W3C_WG_DECISION_URL: https://lists.w3.org/Archives/Public/public-webappsec/2015Mar/0170.html

.gitignore

@@ -0,0 +1 @@
+index.html

Makefile

@@ -1,14 +1,14 @@
 all: index.html
 
 force:
-	bikeshed -f spec ./index.src.html
+	bikeshed -f spec ./index.bs
 
-index.html: index.src.html
-	bikeshed -f spec ./index.src.html
+index.html: index.bs
+	bikeshed -f spec ./index.bs
 
-CR: index.src.html
-	bikeshed -f spec --md-status=CR --md-date=2015-10-08 --md-deadline=2015-11-08 ./index.src.html ./published/2015-10-CR.html
+CR: index.bs
+	bikeshed -f spec --md-status=CR --md-date=2015-10-08 --md-deadline=2015-11-08 ./index.bs ./published/2015-10-CR.html
 
-publish:
-	git push origin master master:gh-pages
+clean:
+	$(RM) index.html