docs: refresh for JS and drop Lua references

- style with clean-jsdoc-theme (supports dark mode)
- add tutorials (jaguar has a problem with this structure)
- move doc gen stubs to doc_gen folder

This change moves the generated JS API docs from /luci/jsapi
to /luci via README.md which forms the index, and shall
point to a generated html file which exists. It currently
points to LuCI.html, which depends on JSDoc naming
conventions. So it's possible the link can break if modules
change names. But the TOC is always valid.

Signed-off-by: Paul Donald <newtwen+github@gmail.com>

doc_gen/extra.css

@@ -0,0 +1,35 @@
+.navbar-item.github-home a {
+	background-image: url("data:image/svg+xml,%3Csvg width='98' height='96' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath fill-rule='evenodd' clip-rule='evenodd' d='M48.854 0C21.839 0 0 22 0 49.217c0 21.756 13.993 40.172 33.405 46.69 2.427.49 3.316-1.059 3.316-2.362 0-1.141-.08-5.052-.08-9.127-13.59 2.934-16.42-5.867-16.42-5.867-2.184-5.704-5.42-7.17-5.42-7.17-4.448-3.015.324-3.015.324-3.015 4.934.326 7.523 5.052 7.523 5.052 4.367 7.496 11.404 5.378 14.235 4.074.404-3.178 1.699-5.378 3.074-6.6-10.839-1.141-22.243-5.378-22.243-24.283 0-5.378 1.94-9.778 5.014-13.2-.485-1.222-2.184-6.275.486-13.038 0 0 4.125-1.304 13.426 5.052a46.97 46.97 0 0 1 12.214-1.63c4.125 0 8.33.571 12.213 1.63 9.302-6.356 13.427-5.052 13.427-5.052 2.67 6.763.97 11.816.485 13.038 3.155 3.422 5.015 7.822 5.015 13.2 0 18.905-11.404 23.06-22.324 24.283 1.78 1.548 3.316 4.481 3.316 9.126 0 6.6-.08 11.897-.08 13.526 0 1.304.89 2.853 3.316 2.364 19.412-6.52 33.405-24.935 33.405-46.691C97.707 22 75.788 0 48.854 0z' fill='%2324292f'/%3E%3C/svg%3E");
+	background-repeat: no-repeat;
+	background-size: 1.5em;
+	background-position: 1rem center;
+	padding-left: 3rem;
+}
+
+.signature-attributes {
+  font-style:italic;
+  font-weight:lighter;
+  font-variant:sub;
+}
+
+span.param-type {
+	color:#00918e;
+}
+
+.type-signature {
+	display: inline-block;
+	color:#00918e;
+}
+
+.type-signature::after {
+	content: ' ';
+}
+
+span.signature::after {
+	content: ' ';
+}
+
+table.props tbody td,
+table.params tbody td {
+	padding: 0.5rem;
+}