dec.html, enc.html: make output textarea read-only

dec.html

@@ -15,7 +15,7 @@
 	<label for="password">Password: </label>
 	<input id="password" type="password">
 	<button id="decrypt">Decrypt</button>
-	<textarea id="plaintext"></textarea>
+	<textarea id="plaintext" readonly></textarea>
 	<script>
 		document.getElementById("decrypt").addEventListener("click", dec);
 	</script>

enc.html

@@ -15,7 +15,7 @@
 	<label for="password">Password: </label>
 	<input id="password" type="password">
 	<button id="encrypt">Encrypt</button>
-	<textarea id="ciphertext"></textarea>
+	<textarea id="ciphertext" readonly></textarea>
 	<script>
 		document.getElementById("encrypt").addEventListener("click", enc);
 	</script>