Auto detect jinja and j2 files as jinja templates

[DonJayamanne]

Fixes #1484

This pull request:

• Has a title summarizes what is changing
• Includes a news entry file (remember to thank yourself!)

[d3r3kk]

Looks fine to me, and learned something new as well (we can break into HTML & template code. Nice touch).

[d3r3kk]

CI has trouble, looks like this line?

prospector 0.12.7 has requirement pycodestyle==2.0.0, but you'll have pycodestyle 2.3.1 which is incompatible. 

[DonJayamanne]

There's a separate issue for that, can be ignored.

[codecov]

Codecov Report

Merging #1575 into master will decrease coverage by 0.22%.
The diff coverage is n/a.

@@ Coverage Diff @@ ## master #1575 +/- ## ========================================== - Coverage 71.65% 71.42% -0.23%  ========================================== Files 273 273 Lines 12700 12700 Branches 2282 2282 ========================================== - Hits 9100 9071 -29  - Misses 3465 3493 +28  - Partials 135 136 +1

Impacted Files	Coverage Δ
src/client/linters/errorHandlers/notInstalled.ts	33.33% <0%> (-61.12%)	⬇️
src/client/linters/errorHandlers/errorHandler.ts	77.77% <0%> (-22.23%)	⬇️
src/client/common/logger.ts	53.33% <0%> (-20.01%)	⬇️
src/client/common/application/applicationShell.ts	23.07% <0%> (-7.7%)	⬇️
src/client/common/installer/productInstaller.ts	60.31% <0%> (-4.24%)	⬇️
src/client/linters/baseLinter.ts	88.54% <0%> (-3.13%)	⬇️
...rc/client/debugger/PythonProcessCallbackHandler.ts	52.96% <0%> (-0.66%)	⬇️
src/client/debugger/mainV2.ts	75.8% <0%> (+0.8%)	⬆️

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