Add back to index link and other changes

Author: tulir

README.md

@@ -3,4 +3,5 @@ This repo contains the documentation for all my Matrix software. The intention
 is to reduce duplication that was present in the old bridge wikis.
 
 The books are built with [mdBook](https://github.com/rust-lang/mdBook).
-The front page in the `bookshelf` directory is based on [docs.t2bot.io](https://github.com/t2bot/docs.t2bot.io).
+The front page in the `bookshelf` directory is based on
+[docs.t2bot.io](https://github.com/t2bot/docs.t2bot.io).

bridges/book.toml

@@ -20,7 +20,7 @@ additional-css = ["src/additional.css"]
 
 [output.linkcheck]
 optional = true
-user-agent = "Mozilla/5.0 (X11; Linux x86_64; rv:86.0) Gecko/20100101 Firefox/86.0"
+user-agent = "Mozilla/5.0 (X11; Linux x86_64; rv:88.0) Gecko/20100101 Firefox/88.0"
 cache-timeout = 604800
 exclude = [ 'developer\.android\.com' ]
 traverse-parent-directories = false

bridges/theme/index.hbs

@@ -103,6 +103,11 @@
 
         <nav id="sidebar" class="sidebar" aria-label="Table of contents">
             <div class="sidebar-scrollbox">
+                <ol class="chapter">
+                    <li class="chapter-item expanded affix">
+                        <a href="https://docs.mau.fi">Back to index</a>
+                    </li>
+                </ol>
                 {{#toc}}{{/toc}}
             </div>
             <div id="sidebar-resize-handle" class="sidebar-resize-handle"></div>