fix: source maps generation

[alexander-akait]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

fix source maps generation without the sourceMap option

Breaking Changes

No

Additional Info

No

[codecov]

Codecov Report

Merging #886 into master will increase coverage by 0.03%.
The diff coverage is 92.85%.

@@            Coverage Diff             @@
##           master     #886      +/-   ##
==========================================
+ Coverage   95.92%   95.96%   +0.03%     
==========================================
  Files           4        4              
  Lines         221      223       +2     
  Branches       70       71       +1     
==========================================
+ Hits          212      214       +2     
  Misses          8        8              
  Partials        1        1              

Impacted Files	Coverage Δ
src/utils.js	95.13% <90.00%> (+0.13%)	⬆️
src/index.js	100.00% <100.00%> (ø)

---

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 b3a1981...18c4059. Read the comment docs.