chore: add comment in Makefile

Author: joshzcold

Makefile

@@ -9,6 +9,7 @@ test: deps test_requirements
 test_file: deps test_requirements
 	nvim --headless --noplugin -u ./scripts/minimal_init.lua -c "lua MiniTest.run_file('$(FILE)')"
 
+# Install all test dependencies
 deps: deps/mini.nvim \
 			deps/nvim-dap \
 			deps/nvim-dap-python \