Update DevelopmentWorkflow.md for v6 #7745

I'm trying to test a contribution to the v6 tns-core-modules and tns-core-modules-widgets, and running into problems following the DevelopmentWorkflow.md. I think it is outdated.

In short, I want to modify a .ts file in tns-core-modules and be able to test the modification in a v6 NativeScript app in another directory.

A few issues with the current DevelopmentWorkflow.md:

1. The initial setup (npm install) does not npm link
2. Running Another App indicates changes require TS rebuild (tsc), however it does not specify which package.json script target to run. My hunch is it is dev-tsc-all but this script has a bug in it (pr below) AND after running, the .js files end up in bin/dist/tns-core-modules/ without a package.json (so npm link will not work). compile-all script does the same.
3. dev-link-tns-core-modules-widgets script references a dist/package dir that DNE.

I'm happy to do the work to PR an update to the docs, however I need some clarity on the right way to do it 1st.

Here is my workflow - what am I doing wrong?

1. Fork and clone
2. git checkout -b my-feature/fix-branch
3. npm install
4. npm run compile-all
5. From root of my NS proj: npm link ../<where I cloned>/tns-core-modules-widgets/ && npm link ../<where I cloned>/tns-core-modules
6. tns debug ios --debug-brk --env.sourceMap