Update HTTP caching rules

lib/app.rb

@@ -78,9 +78,14 @@ class App < Sinatra::Application
       header_rules: [
         [:all,              { 'Cache-Control' => 'no-cache, max-age=0'    }],
         ['/assets',         { 'Cache-Control' => 'public, max-age=604800' }],
+        ['/docs',           { 'Cache-Control' => 'public, max-age=86400'  }],
+        ['/images',         { 'Cache-Control' => 'public, max-age=86400'  }],
         ['/favicon.ico',    { 'Cache-Control' => 'public, max-age=86400'  }],
-        ['/mathml.css',  {'Cache-Control' => 'public, max-age=604800'}],
-        ['/images',      {'Cache-Control' => 'public, max-age=86400'}] ]
+        ['/robots.txt',     { 'Cache-Control' => 'public, max-age=86400'  }],
+        ['/opensearch.xml', { 'Cache-Control' => 'public, max-age=86400'  }],
+        ['/mathml.css',     { 'Cache-Control' => 'public, max-age=86400'  }],
+        ['/manifest.json',  { 'Cache-Control' => 'public, max-age=86400'  }]
+      ]
 
     sprockets.js_compressor = Uglifier.new output: { beautify: true, indent_level: 0 }
     sprockets.css_compressor = :sass