feat(Makefile): Add empty bundle-pre target for customization.

The empty bundle-pre target is run before the bundle target and can be
overwritten in extending projects to add some tasks before bundle generation.
This can be used to unlink and reinstall any dependencies before bundle generation.

Author: thet

Makefile

@@ -35,8 +35,16 @@ check:: stamp-yarn eslint
 	$(YARN) run test
 
 
+bundle-pre:
+	@# Override this in your project to add some tasks before the bundle is built.
+	@# Example: Unlink any linked dependencies.
+	@#     bundle-pre:
+	@#         -yarn unlink @patternslib/patternslib
+	@#         yarn install --force
+
+
 .PHONY: bundle
-bundle: stamp-yarn
+bundle: bundle-pre stamp-yarn
 ifneq "$(PACKAGE_NAME)" "$(PACKAGE_DEV)"
 	@# Do not build a bundle for @patternslib/dev
 	$(YARN) run build