chore: add visual tests

[layershifter]

This PR adds a visual testing step via Percy to avoid visual regressions in future (#4092, #4083).

[github-actions]

size-limit report

Path	Size
bundle-size/dist/Button.size.js	58.65 KB (0%)
bundle-size/dist/Icon.size.js	25.06 KB (0%)
bundle-size/dist/Image.size.js	53.83 KB (0%)
bundle-size/dist/Modal.size.js	68.73 KB (0%)
bundle-size/dist/Portal.size.js	40.54 KB (0%)

[codecov-io]

Codecov Report

Merging #4093 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4093   +/-   ##
=======================================
  Coverage   99.75%   99.75%           
=======================================
  Files         180      180           
  Lines        3231     3231           
=======================================
  Hits         3223     3223           
  Misses          8        8           

---

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 1fbeed9...21c165c. Read the comment docs.