file upload preparations

html/chat.html

@@ -1,6 +1,12 @@
 <form id="chat" autocomplete="off" onsubmit="sendmessage(this.elements['recv'].value, this.elements['msg'].value)">
   <input placeholder="receiver" autocomplete="off" type="text" id="recv" oninput="checkpartner(this.value)" />
   <input placeholder="message" autocomplete="off" type="text" id="msg"/>
+  <label class="icon" for="file" style="flex-grow: 0"><img style="width: 2em; height: 2em" src="attachment.svg"/></label>
+  <input class="icon" autocomplete="off" type="file" id="file" style="display:none"/>
   <input type="submit" id="send" disabled/>
 </form>
 <div id="msgs"></div>
+<script>
+  $("#file").change(function(evt){fileupload(evt)});
+  if (!window.FileReader) $("#file").hide(); // not supported by browser
+</script>