chore: enforce minimum coder server version of v2.20.0 (#90)

This will cause Coder Desktop networking to fail to start unless the validated dylib is version `v2.20.0` or later. Obviously, using this build early would mean Coder Desktop would not work against our dogfood deployment.

chore: add dark menu bar icon (#49)

fix(Makefile): add version validation checks (#44)

Signed-off-by: Thomas Kosiewski <tk@coder.com>