feat(tsconfig): add support for custom typescript config

[iammathew]

Hey,

this MR tries to fix oclif/oclif#299 by adding a ENV to set a custom typescript config, nothing special, but enables users to set a custom tsconfig in development scenarios.

Cooler would be to be able to set it inside the oclif config, but as the ts-node module right now doesnt need to access it i didnt want to introduce a "dependency" there.

Let me know how I can improve this MR

[codecov]

Codecov Report

Merging #152 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #152   +/-   ##
======================================
  Coverage    0.00%   0.00%           
======================================
  Files           2       2           
  Lines          12      12           
  Branches        3       3           
======================================
  Misses         12      12           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f3ea593...c205e43. Read the comment docs.

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @khayalan-mathew to sign the Salesforce.com Contributor License Agreement.

[iammathew]

@RasPhilCo @amphro
Sorry for not signing the CLA earlier, let me know what you think of it, so i can improve it :)

[amphro]

Seems simple enough. Out of curiosity, what are the development scenarios you talked about?

[iammathew]

@amphro Im running oclif inside a nx workspace, right now i need to change a bit in the tsconfig to make the /bin/run working with typescript, this conflicts with the overall workspace rules, and some advanced behaviors like importing other packages using paths cause issues with the modifications oclif needs.

Hope that clears that up.

[humandad]

I'm also trying to use oclif with nx and would appreciate this feature. Is there anything blocking this?

[iammathew]

@humandad Waiting for feedback, atm. But hopefully this can be merged soon :)