Include Flic button Linux SDK for access to Node library

It's a lot of bloat for one file, but I'd rather do this and keep in sync with Flic's releases.

.gitmodules

+[submodule "vendor/fliclib-linux-hci"]
+	path = vendor/fliclib-linux-hci
+	url = https://github.com/50ButtonsEach/fliclib-linux-hci.git

fliclib-linux-hci @ e68fab52

+Subproject commit e68fab52a2bbdada2f38dd5139626cd0c7180fb7