jekyll: move jekyll back to root, but simpler setup, exclude via _config.yml

app: bundle jekyll docs into app, add 'yarn run docs' to build
ui: add back/forward arrows for app only, adjust responsiveness for app, add IS_APP flag injected via preload
ui: add animated logo, friendly message on empty replay frame
app: improve serve logic:
- serve static files from static root
- serve replay from http localhost instead to avoid proxying https for remote requests
- serve local lookup from http prefix also
- catch any fallthrough from replay as 404
- add timestamp to response channels to ensure uniqness

_includes/title.html

@@ -0,0 +1,5 @@
+{% if site.logo %}
+  <div class="site-logo"></div>
+{% endif %}
+<span class="rwp-logo-font rwp-green">replay</span>
+<span class="rwp-logo-font rwp-blue">web.page</span>