Fetch test/javascript when creating Devcontainer

[ankddev]

Closes #138

Description

I've updated postCreate.sh script to firstly check origin and if it's equal to https://github.com/spenserblack/gengo, run git fetch origin test/javascript:test/javascript, else git fetch upstream test/javascript:test/javascript

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.59%. Comparing base (ac6dcca) to head (f33f7e6).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #525   +/-   ##
=======================================
  Coverage   71.59%   71.59%           
=======================================
  Files          18       18           
  Lines         521      521           
=======================================
  Hits          373      373           
  Misses        148      148           

Flag	Coverage Δ
--no-default-features	72.63% <ø> (ø)
--no-default-features --features color	71.20% <ø> (ø)
ubuntu-latest	71.59% <ø> (ø)

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[spenserblack]

I think it would be better to unconditionally add a remote and fetch from it instead. Check out how github-linguist does it.