Quick frontend channel search

[cheeseblubber]

In large communities it is difficult to browse and find channels we should have a simple frontend filter to search through the channels on the left side

Context: https://slack-chats.kotlinlang.org/t/13226465/i-love-that-i-can-point-anyone-to-this-slack-using-http-line#b1826f15-731d-47d6-9d75-e3808b697769

First comment about channel navigation