[WIP] Add / remove declaration in preview

[ktsn]

This PR allows the users to add or remove css declaration in preview.

I've only implemented the code modifier to add / remove declaration code yet. I'll make it works in the preview as well later.

Also, it would be needed to update css codegen to output pretty code since we may use it for modifying the original code.

[codecov]

Codecov Report

Merging #11 into master will decrease coverage by 0.76%.
The diff coverage is 50%.

@@            Coverage Diff             @@
##           master      #11      +/-   ##
==========================================
- Coverage   63.85%   63.09%   -0.77%     
==========================================
  Files          40       40              
  Lines        1256     1306      +50     
  Branches      308      313       +5     
==========================================
+ Hits          802      824      +22     
- Misses        441      467      +26     
- Partials       13       15       +2

Impacted Files	Coverage Δ
src/view/components/PageMain.vue	0% <ø> (ø)	⬆️
src/parser/style/codegen.ts	88.88% <ø> (ø)	⬆️
src/view/components/StyleInformation.vue	0% <0%> (ø)	⬆️
src/server/main.ts	0% <0%> (ø)	⬆️
src/message/bus.ts	0% <0%> (ø)	⬆️
src/view/components/StyleValue.vue	100% <100%> (ø)	⬆️
src/parser/modifier.ts	88.46% <100%> (+0.46%)	⬆️
src/view/store/modules/project.ts	39.58% <20%> (-1.14%)	⬇️
src/parser/style/transform.ts	83.51% <83.33%> (-0.02%)	⬇️
src/parser/style/modify.ts	89.47% <89.47%> (-10.53%)	⬇️

---

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 d0dbac0...f5b9a26. Read the comment docs.