🏎️ make: Fix prettier installation race (#463)

Targets `docs`, `learn` and `labs` all use prettier which gets installed with

    npx --prefix $(NODEPREFIX) -y prettier # ...

Occasionally this seems to fail on CI when run concurrently. Fix by adding an
explicit dependency and prettier installation and a `.WAIT`.

Pull-request: #463

Author: juliaogris

Makefile

@@ -21,7 +21,7 @@ lint: lint-go lint-sh lint-node check-fmt-evy conform
 ## Full clean build and up-to-date checks as run on CI for local execution
 ci: check-uptodate .WAIT all
 
-check-uptodate: clean .WAIT tidy fmt doc docs learn lab
+check-uptodate: clean .WAIT install-npm-deps .WAIT tidy fmt doc docs learn lab
 	test -z "$$(git status --porcelain)" || { git status; false; }
 
 ## Remove generated files