Added web-middleware based theme events

app/Http/Middleware/RunThemeActions.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace BookStack\Http\Middleware;
+
+use BookStack\Facades\Theme;
+use BookStack\Theming\ThemeEvents;
+use Closure;
+
+class RunThemeActions
+{
+    /**
+     * Handle an incoming request.
+     *
+     * @param  \Illuminate\Http\Request  $request
+     * @param  \Closure  $next
+     * @return mixed
+     */
+    public function handle($request, Closure $next)
+    {
+        $earlyResponse = Theme::dispatch(ThemeEvents::WEB_MIDDLEWARE_BEFORE, $request);
+        if (!is_null($earlyResponse)) {
+            return $earlyResponse;
+        }
+
+        $response = $next($request);
+        $response = Theme::dispatch(ThemeEvents::WEB_MIDDLEWARE_AFTER, $request, $response) ?? $response;
+        return $response;
+    }
+}