fix: resolution algorithm

[alexander-akait]

This PR contains a:

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

Motivation / Use-Case

Fix resolve logic:

• resolve _name when you use @import "name"
• resolve index and _index when you use @import "name" or @import "_name" and name/_name are directory
• resolve index and _index when you use @import "sub/name" or @import "sub/_name" and name/_name are directory

Breaking Changes

No

Additional Info

Potentially can increase compilation time, we will avoid this in future major release, now it is impossible due we need keep compatibility

[codecov]

Codecov Report

Merging #720 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #720   +/-   ##
=======================================
  Coverage   95.15%   95.15%           
=======================================
  Files           7        7           
  Lines         165      165           
  Branches       50       50           
=======================================
  Hits          157      157           
  Misses          8        8

Impacted Files	Coverage Δ
src/index.js	93.42% <ø> (ø)	⬆️
src/importsToResolve.js	100% <100%> (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 96f436f...b59abe5. Read the comment docs.