Use versions.json method for sphinx-material

Otherwise don't think we can get links working on nested pages

Notably this usually won't work locally - see
https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS/Errors/CORSRequestNotHttp

Author: honno

spec/Makefile

@@ -25,6 +25,7 @@ clean:
 
 build:
 	-mkdir -p $(BUILDDIR)
+	-cp "$(SOURCEDIR)/versions.json" "$(BUILDDIR)/versions.json"
 	-sphinx-build "$(SOURCEDIR)/2021.12" "$(BUILDDIR)/2021.12"
 	-cp -r "$(BUILDDIR)/2021.12" "$(BUILDDIR)/latest"
 	-sphinx-build "$(SOURCEDIR)/draft" "$(BUILDDIR)/draft"

spec/versions.json

@@ -0,0 +1,5 @@
+{
+	  "2021.12": "2021.12",
+	  "latest": "latest",
+	  "draft": "draft"
+}

src/_spec_conf.py

@@ -173,7 +173,7 @@
     },
 
     "version_dropdown": True,
-    "version_info": {v: f"../{v}" for v in ["2021.12", "latest", "draft"]},
+    "version_json": "../versions.json",
     "table_classes": ["plain"],
 }