rewrite pattern for tag, should starts with [aA-zZ]

Author: dimaspirit

samples/webrtc/index.html

@@ -39,11 +39,11 @@ <h3 class="join__title">
 
                     <div class="join__body">
                         <div class="join__row">
-                            <input type="text" class="join__input" name="username" placeholder="Username" autofocus required title="Should contain only latin characters and alphanumeric characters in a range from 3 to 20, starts with a letter." pattern="^[a-zA-Z][a-zA-Z0-9-_\.]{1,20}$">
+                            <input type="text" class="join__input" name="username" placeholder="Username" autofocus required title="Should contain only latin characters and alphanumeric characters in a range from 3 to 20, starts with a letter." pattern="^[a-zA-Z][a-zA-Z0-9-_\.]{3,20}$">
                         </div>
 
                         <div class="join__row">
-                            <input type="text" class="join__input" name="room" placeholder="Chat room name" required title="Should contain only latin characters and alphanumeric characters in a range from 3 to 15, without space." pattern="^[a-zA-Z0-9]{3,15}">
+                            <input type="text" class="join__input" name="room" placeholder="Chat room name" required title="Should contain only latin characters and alphanumeric characters in a range from 3 to 15, without space." pattern="^[a-zA-Z][a-zA-Z0-9]{3,15}">
                         </div>
 
                         <div class="join__row">