feat: convert input to type search

This type of input has an [x] on the right side to clear input
instantly. Key ESC binds to this automatically. Had to add onsearch to
this input too.

Signed-off-by: Conrad Zelck <git@simpel.cc>

index.php

@@ -25,7 +25,7 @@
     <main>
       <div>
         <label for="searchinput">Search language or comment syntax:</label>
-        <input type="text" id="searchinput" onkeyup="searchSyntax()" title="Type in a scripting language or comments syntax" placeholder="search string …" autofocus>
+        <input type="search" id="searchinput" onkeyup="searchSyntax()" onsearch="searchSyntax()" title="Type in a scripting language or comments syntax" placeholder="search string …" autofocus>
         <table id="resulttable">
           <thead>
             <tr>

style.css

@@ -97,7 +97,7 @@ input {
   box-sizing: border-box;
 }
 
-input[type="text"] {
+input[type="search"] {
   width: 70ch;
   max-width: calc(100vw - 8vmin);
 }