* Remove Makefile from all intree extensions
- Makefiles are not really common (rightly so) in JS projects and script
entries in the package.json are good enough and what they're there
for.
- Move to using yarn for installing dependencies and running scripts as
that is what we mostly use for the rest of the project.
- Move from using make syntax to a dedicated script for building and
testing extensions.
- add jest as extension devDep, go back to using makefile foreach syntax
- add correct exit code
- add yarn check call to install-deps
- add yarn invokation to find deps
Signed-off-by: Sebastian Malton <sebastian@malton.name>
