feat: support yaml with ${env.variable}

[czy88840616]

No description provided.

[gitpod-io]

[codecov-io]

Codecov Report

Merging #157 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #157      +/-   ##
==========================================
+ Coverage   80.28%   80.30%   +0.01%     
==========================================
  Files          85       85              
  Lines        3181     3184       +3     
  Branches      357      358       +1     
==========================================
+ Hits         2554     2557       +3     
  Misses        623      623              
  Partials        4        4              

Impacted Files	Coverage Δ
packages/serverless-spec-builder/src/index.ts	92.30% <100.00%> (+1.00%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 85824ee...ea0fe11. Read the comment docs.