fix: a11y R4 time template for relative timestamps (#554)

deploy/gitea-a11y/custom/templates/custom/time_relative.tmpl

@@ -0,0 +1,27 @@
+{{/*
+  Gitea a11y fix: R4 <time> elements for relative timestamps
+  Deploy to: custom/templates/custom/time_relative.tmpl
+*/}}
+
+{{define "custom/time_relative"}}
+{{if and .Time .Relative}}
+<time datetime="{{.Time.Format "2006-01-02T15:04:05Z07:00"}}" title="{{.Time.Format "Jan 02, 2006 15:04"}}">
+  {{.Relative}}
+</time>
+{{else if .Relative}}
+<span>{{.Relative}}</span>
+{{end}}
+{{end}}
+
+{{define "custom/time_from_unix"}}
+{{if .Relative}}
+<time datetime="" data-unix="{{.Unix}}" title="">{{.Relative}}</time>
+<script>
+(function() {
+  var el = document.currentScript.previousElementSibling;
+  var unix = parseInt(el.getAttribute('data-unix'));
+  if (unix) { el.setAttribute('datetime', new Date(unix * 1000).toISOString()); el.setAttribute('title', new Date(unix * 1000).toLocaleString()); }
+})();
+</script>
+{{end}}
+{{end}}