HY-4965 Turn on strong mode and 2 lint rules

[robbecker-wf]

This turns on strong mode and adds 2 lint rules to make sure streams are closed.

[aviary-wf]

Raven

Number of Findings: 0

[codecov-io]

Codecov Report

Merging #44 into master will decrease coverage by 3.57%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #44      +/-   ##
==========================================
- Coverage   96.42%   92.85%   -3.58%     
==========================================
  Files           1        1              
  Lines          28       28              
==========================================
- Hits           27       26       -1     
- Misses          1        2       +1

Impacted Files	Coverage Δ
lib/dart_to_js_script_rewriter.dart	92.85% <0%> (-3.58%)	⬇️

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[smaifullerton-wk]

+1

[maxwellpeterson-wf]

+10

• CI passes

[maxwellpeterson-wf]

QA +1

• Dev +1's
• Dev/QA +10 with detail of what was tested
• Tests created/updated
  • Tooling only
• All tests pass

@Workiva/release-management-pp