adds show/hide all button (#319)

resolves https://github.com/amiaopensource/ffmprovisr/issues/211

index.html

@@ -19,6 +19,7 @@
   <nav class="sidebar well">
     <h2 class="heading">Table of Contents</h2>
     <a href="#about"><div class="contents-list">About this resource</div></a>
+    <div id="open-all" class="contents-list">Show/hide all recipes</div>
     <a href="#basics"><div class="contents-list">FFmpeg basics</div></a>
     <a href="#concepts"><div class="contents-list">Advanced FFmpeg concepts</div></a>
     <a href="#rewrap"><div class="contents-list">Change container (rewrap)</div></a>
@@ -47,6 +48,7 @@
       <span class="intro-lead">Making FFmpeg Easier</span>
       <p>FFmpeg is a powerful tool for manipulating audiovisual files. Unfortunately, it also has a steep learning curve, especially for users unfamiliar with a command line interface. This app helps users through the command generation process so that more people can reap the benefits of FFmpeg.</p>
       <p>Each button displays helpful information about how to perform a wide variety of tasks using FFmpeg. To use this site, click on the task you would like to perform. A new window will open up with a sample command and a description of how that command works. You can copy this command and understand how the command works with a breakdown of each of the flags.</p>
+      <p>This page does not have search functionality, but you can open all recipes (second option in the sidebar) and use your browser's search tool (often ctrl+f or cmd+f) to perform a keyword search through all recipes.</p>
       <span class="intro-lead">Tutorials</span>
       <p>For FFmpeg basics, check out the program’s <a href="https://ffmpeg.org/" target="_blank">official website</a>.</p>
       <p>For instructions on how to install FFmpeg on Mac, Linux, and Windows, refer to Reto Kromer’s <a href="https://avpres.net/FFmpeg/#ch1" target="_blank">installation instructions</a>.</p>