feat: support updating style declaration in preview

[ktsn]

This feature allows us to edit styles in the preview pane like chrome devtools but it immediately update the original code in SFC.

I'll add more test and support renaming declaration prop later.

Adding declaration is not supported yet.

[codecov-io]

Codecov Report

Merging #6 into master will increase coverage by 0.51%.
The diff coverage is 69.01%.

@@            Coverage Diff             @@
##           master       #6      +/-   ##
==========================================
+ Coverage   63.65%   64.17%   +0.51%     
==========================================
  Files          34       36       +2     
  Lines        1175     1242      +67     
  Branches      283      298      +15     
==========================================
+ Hits          748      797      +49     
- Misses        414      432      +18     
  Partials       13       13

Impacted Files	Coverage Δ
src/parser/style/codegen.ts	88.88% <ø> (ø)	⬆️
src/view/components/PageMain.vue	0% <ø> (ø)	⬆️
src/message/bus.ts	0% <0%> (ø)	⬆️
src/view/components/StyleInformation.vue	0% <0%> (ø)	⬆️
src/parser/vue-file.ts	0% <0%> (ø)	⬆️
src/server/main.ts	0% <0%> (ø)	⬆️
src/parser/style/manipulate.ts	90% <100%> (+8.18%)	⬆️
src/parser/style/transform.ts	83.52% <100%> (ø)	⬆️
src/view/components/StyleValue.vue	100% <100%> (ø)
src/parser/modifier.ts	92.7% <100%> (+0.31%)	⬆️
... and 5 more

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