Header: Add role=search to search forms

Author: Turbo87

app/components/header.hbs

@@ -5,7 +5,7 @@
       <h1>crates.io</h1>
     </LinkTo>
 
-    <form local-class="desktop-search-form" action='/search' {{on "submit" (prevent-default this.search)}} data-test-search-form>
+    <form local-class="desktop-search-form" action='/search' role="search" {{on "submit" (prevent-default this.search)}} data-test-search-form>
       {{! template-lint-disable require-input-label}}
       {{! disabled due to https://github.com/ember-template-lint/ember-template-lint/issues/2141 }}
       <input
@@ -145,7 +145,7 @@
       </Dropdown>
     </div>
 
-    <form local-class='mobile-search' action='/search' {{on "submit" (prevent-default this.search)}}>
+    <form local-class='mobile-search' action='/search' role="search" {{on "submit" (prevent-default this.search)}}>
       <input
         type="text"
         local-class="search"