Adding demo.asciinema.json to gitignore (#221)

It is generated when $ make gen-demo is run

Signed-off-by: Lalatendu Mohanty <[email protected]>

Author: LalatenduMohanty

.gitignore

@@ -28,3 +28,6 @@ dist/
 
 # Session
 Session.vim
+
+#asciicinema
+assets/demo/demo.asciinema.json