message: Add tabindex to "Find crate" text input in rustdoc navigation
  Closes:
diff: <div class="pure-menu pure-menu-horizontal">
  <form action="/releases/search" method="GET" class="landing-search-form-nav">
  {{#unless varsb.show_search_form}}
  - <input class="search-input-nav" name="query" type="text" placeholder="Find crate"{{#if varss.search_query}} value="{{varss.search_query}}"{{/if}}>
  + <input class="search-input-nav" name="query" tabindex="-1" type="text" placeholder="Find crate"{{#if varss.search_query}} value="{{varss.search_query}}"{{/if}}>
  {{/unless}}
  <a href="/" class="pure-menu-heading pure-menu-link"><i class="fa fa-cubes fa-fw"></i><span class="title"> Docs.rs</span></a>
  {{#with content.metadata}}
  