Improve the precision of alpha values

[omgovich]

During the work on cssnano/cssnano#1109 we figured out that, for example, rgba(0, 0, 0, 0.55) and rgba(0, 0, 0, 0.555) are perceived differently. So I decided to update the library to output more accurate alpha values by default.

[github-actions]

Size Change: -3 B (0%)

Total Size: 8.98 kB

Filename	Size	Change
./dist/index.js	2.01 kB	+7 B (0%)
./dist/plugins/hwb.js	890 B	-1 B (0%)
./dist/plugins/lab.js	1.03 kB	+1 B (0%)
./dist/plugins/lch.js	1.42 kB	-10 B (-1%)

ℹ️ View Unchanged

Filename	Size	Change
./dist/plugins/a11y.js	459 B	0 B
./dist/plugins/mix.js	956 B	0 B
./dist/plugins/names.js	1.39 kB	0 B
./dist/plugins/xyz.js	833 B	0 B

_{compressed-size-action}

[codecov-commenter]

Codecov Report

Merging #55 (775599f) into master (941ccf0) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #55   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           34        35    +1     
  Lines          425       435   +10     
  Branches        94        94           
=========================================
+ Hits           425       435   +10     

Impacted Files	Coverage Δ
src/colorModels/hex.ts	100.00% <100.00%> (ø)
src/colorModels/hsl.ts	100.00% <100.00%> (ø)
src/colorModels/hsv.ts	100.00% <100.00%> (ø)
src/colorModels/hwb.ts	100.00% <100.00%> (ø)
src/colorModels/lab.ts	100.00% <100.00%> (ø)
src/colorModels/lch.ts	100.00% <100.00%> (ø)
src/colorModels/rgb.ts	100.00% <100.00%> (ø)
src/colorModels/xyz.ts	100.00% <100.00%> (ø)
src/colord.ts	100.00% <100.00%> (ø)
src/constants.ts	100.00% <100.00%> (ø)
... and 2 more

---

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 941ccf0...775599f. Read the comment docs.