Add rich presence example (#880)

Author: mikasa

examples/rich_presence.py

@@ -0,0 +1,42 @@
+import discord
+
+# Your Developer Portal Application ID (used for proxying external assets)
+APPLICATION_ID = 123456789012345678
+
+# Any direct image URLs (png/jpg/gif). Discord will proxy these.
+LARGE_IMAGE_URL = 'image url here'
+SMALL_IMAGE_URL = 'image url here'
+
+
+class MyClient(discord.Client):
+    async def on_ready(self):
+        # Proxy BOTH urls in one call (Discord supports proxying up to 2 at a time).
+        proxied_large, proxied_small = await self.proxy_external_application_assets(
+            APPLICATION_ID,
+            LARGE_IMAGE_URL,
+            SMALL_IMAGE_URL,
+        )
+
+        activity = discord.Activity(
+            type=discord.ActivityType.playing,
+            application_id=APPLICATION_ID,
+            name='name',
+            details='details',
+            state='state',
+            assets=discord.ActivityAssets(
+                large_image=proxied_large,
+                large_text='large_text',
+                small_image=proxied_small,
+                small_text='small_text',
+            ),
+            buttons=[
+                discord.ActivityButton('Website', 'https://example.com'),
+            ],
+        )
+
+        await self.change_presence(status=discord.Status.online, activity=activity)
+        print(f'Rich presence applied as {self.user} ({self.user.id})')
+
+
+client = MyClient()
+client.run('token')