send: change wording, use note instead of post

In nostr we write notes, not posts no tweets just notes.

src/index.html

@@ -28,7 +28,7 @@
             <div id="newMessage" hidden>
               <form action="#" id="writeForm" class="form-inline">
                 <fieldset>
-                  <legend>write a new post</legend>
+                  <legend>write a new note</legend>
                   <textarea name="message" rows="1"></textarea>
                   <div class="buttons">
                     <button type="submit" id="publish" disabled>send</button>