chore(build): more local tsc build

[elmerbulthuis]

Adds a more localized build setup to the jco package

The jco project now has a tsc script that compiles the project it belongs to. The root project now calls this script.

Also it uses the --build flag wich results in a tsconfig.tsbuildinfo file that will speed up repeated builds by only building the files that changed.

This is a way to a cleaner and easier to understand build architecture. Every project contains everything it needs to build itself, including tasks that can be used to build the project. This PR provides a missing task (tsc) for the jco project. Now we have a way of executing project local tasks in a generic way per environment (in this case, the npm environment).

Then there is a root build system, xtask in our case, that executes those tasks in the right order. In this case there is a root build tasks that compiles all js repositories. It's a pretty simple task now, it just executes the tsc tasks in all projects (1 at the moment). But this could be more complex in the future.

This is in preparation for moving the codebase to TypeScript, see #717.