port over base HTML layout from PHP to FastAPI+Jinja2

+ Mounted static files (at web/html) to /static.
+ Added AURWEB_VERSION to aurweb.config (this is used around HTML
  to refer back to aurweb's release on git.archlinux.org), so we
  need it easily accessible in the Python codebase.
+ Implemented basic Jinja2 partials to put together whole aurweb
  pages. This may be missing some things currently and is a WIP
  until this set is ready to be merged.
+ Added config [options] aurwebdir = YOUR_AUR_ROOT; this configuration
  option should specify the root directory of the aurweb project.
  It is used by various parts of the FastAPI codebase to target
  project directories.

Added routes via aurweb.routers.html:
    * POST /language: Set your session language.
    * GET /favicon.ico: Redirect to /static/images/favicon.ico.
        * Some browsers always look for $ROOT/favicon.ico to get an icon
          for the page being loaded, regardless of a specified "shortcut
          icon" given in a <link> directive.
    * GET /: Home page; WIP.

* Updated aurweb.routers.html.language passes query parameters to
  its next redirection.

When calling aurweb.templates.render_template, the context passed should
be formed via the aurweb.templates.make_context. See
aurweb.routers.html.index for an example of this.

Signed-off-by: Kevin Morris <kevr@0cost.org>

templates/partials/typeahead.html

@@ -0,0 +1,30 @@
+<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script>
+<script type="text/javascript" src="/static/js/bootstrap-typeahead.min.js"></script>
+<script type="text/javascript">
+    $(document).ready(function() {
+        $('#pkgsearch-field').typeahead({
+            source: function(query, callback) {
+                $.getJSON('/rpc', {type: "suggest", arg: query}, function(data) {
+                        callback(data);
+                    });
+                },
+                matcher: function(item) { return true; },
+                sorter: function(items) { return items; },
+                menu: '<ul class="pkgsearch-typeahead"></ul>',
+                items: 20,
+                updater: function(item) {
+                document.location = '/packages/' + item;
+                return item;
+            }
+        }).attr('autocomplete', 'off');
+
+        $('#pkgsearch-field').keydown(function(e) {
+            if (e.keyCode == 13) {
+                var selectedItem = $('ul.pkgsearch-typeahead li.active');
+                if (selectedItem.length == 0) {
+                        $('#pkgsearch-form').submit();
+                }
+            }
+        });
+    });
+</script>