fix(cli,action): when process fails, make exit code 1

[TomKristie]

Assumptions: To my knowledge, in order to get a step to fail, the process exit code has to be 1: https://docs.github.com/en/actions/creating-actions/setting-exit-codes-for-actions

Scenario:

Currently when the node process fails, it always exits with code 0.

Tested by running local script:

if code-suggester pr \
--upstream-repo="dne" \
--upstream-owner="TomKristie" \
--description="describe" \
--title="title" \
--branch="something" \
--primary="master" \
--message="some message" \
--git-dir="./kubernetes"; then
    exit 0
else
    echo "failure exit code non-zero"
    exit 1
fi

which tries to fork a non-existent repo.

The output is

{"level":30,"time":1597342089072,"pid":8411,"hostname":"penguin","msg":"Starting GitHub PR workflow..."}
{"level":50,"time":1597342089474,"pid":8411,"hostname":"penguin","msg":"Error when forking"}
{"level":50,"time":1597342089474,"pid":8411,"hostname":"penguin","msg":"Workflow failed"}
{"level":50,"time":1597342089474,"pid":8411,"hostname":"penguin","stack":"Error: HttpError: Not Found\n    at Object.fork (/home/kristietom/code-suggester/build/src/github-handler/fork-handler.js:44:15)\n    at processTicksAndRejections (internal/process/task_queues.js:97:5)\n    at async Object.createPullRequest (/home/kristietom/code-suggester/build/src/index.js:59:20)\n    at async Object.main (/home/kristietom/code-suggester/build/src/bin/workflow.js:42:17)","type":"Error","msg":"HttpError: Not Found"}
failure exit code non-zero

Fixes #72 🦕

[codecov]

Codecov Report

Merging #81 into master will decrease coverage by 0.48%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master      #81      +/-   ##
==========================================
- Coverage   86.35%   85.86%   -0.49%     
==========================================
  Files          14       14              
  Lines        1231     1238       +7     
  Branches       81       81              
==========================================
  Hits         1063     1063              
- Misses        167      174       +7     
  Partials        1        1              

Impacted Files	Coverage Δ
src/bin/code-suggester.ts	0.00% <0.00%> (ø)

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