Create cache directory

Makefile

@@ -42,7 +42,7 @@ doctor:  ## Confirm system dependencies are available
 DEPENDENCIES := $(VIRTUAL_ENV)/.poetry-$(shell bin/checksum pyproject.toml poetry.lock)
 
 .PHONY: install
-install: $(DEPENDENCIES)
+install: $(DEPENDENCIES) .cache
 
 $(DEPENDENCIES): poetry.lock
 	@ poetry config settings.virtualenvs.in-project true
@@ -53,6 +53,9 @@ poetry.lock: pyproject.toml
 	poetry lock
 	@ touch $@
 
+.cache:
+	@ mkdir -p .cache
+
 # CHECKS ######################################################################
 
 .PHONY: format