#911 Enhance command sysl pb --mode=pb to output binary message

[ericzhang6222]

• Please attach WIP tag when this PR is still work in progress.
• Please attach breaking-change tag if this PR potentially causes other components to fail or changes previous sysl executable's behaviour.

Fixes #911 .

Changes proposed in this pull request:

• Enhance command sysl pb --mode=pb to output binary message

Checklist:

• Added related tests
• Made corresponding changes to the documentation

[codecov]

Codecov Report

Merging #912 into master will increase coverage by 0.02%.
The diff coverage is 81.96%.

@@            Coverage Diff             @@
##           master     #912      +/-   ##
==========================================
+ Coverage   83.35%   83.37%   +0.02%     
==========================================
  Files          73       73              
  Lines       10609    10648      +39     
==========================================
+ Hits         8843     8878      +35     
- Misses       1432     1436       +4     
  Partials      334      334              

Impacted Files	Coverage Δ
pkg/parse/listener_impl.go	89.59% <62.50%> (+0.08%)	⬆️
pkg/mod/gomod.go	73.68% <66.66%> (+1.27%)	⬆️
pkg/pbutil/output.go	76.00% <75.00%> (-0.48%)	⬇️
pkg/importer/openapi.go	88.95% <80.00%> (-0.50%)	⬇️
pkg/diagrams/diagutil.go	62.31% <100.00%> (ø)
pkg/importer/utils.go	88.23% <100.00%> (+0.35%)	⬆️
...g/mermaid/integrationdiagram/integrationdiagram.go	86.66% <100.00%> (+2.29%)	⬆️
pkg/mod/module.go	67.56% <100.00%> (+1.85%)	⬆️

[orlade-anz]

Fair enough.