Minor doc updates, fixes and improvements

In particular, removed code which no longer worked, made light
theme easier on the eyes, added slight syntax highlightning,
and fixed search for exact matches.

readthedocs/extra/examples/telegram-client.rst

@@ -447,34 +447,25 @@ However, a day is often more than enough.
 Sending Messages with Buttons
 *****************************
 
-You must sign in as a bot in order to add inline buttons (or normal
+**You must sign in as a bot** in order to add inline buttons (or normal
 keyboards) to your messages. Once you have signed in as a bot specify
 the `Button <telethon.tl.custom.button.Button>` or buttons to use:
 
 .. code-block:: python
 
+    from telethon import events
     from telethon.tl.custom import Button
 
-    async def callback(event):
-        await event.edit('Thank you!')
-
-    client.send_message(chat, 'Hello!',
-                        buttons=Button.inline('Click me', callback))
-
-
-You can also add the event handler yourself, or change the data payload:
-
-.. code-block:: python
-
-    from telethon import events
-
     @client.on(events.CallbackQuery)
-    async def handler(event):
-        await event.answer('You clicked {}!'.format(event.data))
+    async def callback(event):
+        await event.edit('Thank you for clicking {}!'.format(event.data))
 
-    client.send_message(chat, 'Pick one', buttons=[
+    client.send_message(chat, 'A single button, with "clk1" as data',
+                        buttons=Button.inline('Click me', b'clk1'))
+
+    client.send_message(chat, 'Pick one from this grid', buttons=[
         [Button.inline('Left'), Button.inline('Right')],
-        [Button.url('Check my site!', 'https://lonamiwebs.github.io')]
+        [Button.url('Check this site!', 'https://lonamiwebs.github.io')]
     ])
 
 You can also use normal buttons (not inline) to request the user's