docs: add simple Formula installation instructions

- so that any folks that stumble upon here and don't necessarily remember Homebrew conventions off the top of their head will know what to do!
  - and to remind myself in the future too, of course!

Author: agilgur5

README.md

@@ -1,2 +1,9 @@
 # homebrew-tap
-A personal Tap with Formulae of tools I use that aren't compatible with homebrew-core for various reasons
+
+A personal Tap with Formulae of tools I use that aren't compatible with homebrew-core for various reasons.
+
+A Formula found here can be installed with the following command:
+
+```sh
+brew install agilgur5/tap/<formula>
+```