[BUG] "available_on" filter options not shown for mobile browsers

[rviscomi]

Describe the bug
It's not clear how to filter on mobile browser support

To Reproduce
Steps to reproduce the behavior:

1. Go to https://webstatus.dev/
2. Click on the search input field
3. Look for available_on options for mobile browsers

Expected behavior
The list of available_on filter options includes the syntax for mobile browsers: chrome_android, safari_ios, firefox_android

Screenshots