Enable installing a specific version of ktlint via brew

[martin-tarjanyi]

Expected Behavior

I would like to be able to install a specific version of ktlint via brew so that I can reliably and consistently setup my development environment. New versions of ktlint might contain new rules which without disabling can cause some unwanted changes/failures.

Current Behavior

brew install ktlint currently installs the latest version, there is no option to select a specific version