feat: allow to update numeric style value by pressing up / down key

[ktsn]

ref #13

This allows the users to update numeric style value by pressing up / down key just like Chrome dev tools.

I wrote very naive style value parser for that. And the range analyzation is quite naive also. But I find it just works in the case.

[ktsn]

[codecov]

Codecov Report

Merging #70 into master will increase coverage by 0.45%.
The diff coverage is 72.61%.

@@            Coverage Diff             @@
##           master      #70      +/-   ##
==========================================
+ Coverage   66.97%   67.42%   +0.45%     
==========================================
  Files          65       66       +1     
  Lines        2083     2229     +146     
  Branches      426      449      +23     
==========================================
+ Hits         1395     1503     +108     
- Misses        670      706      +36     
- Partials       18       20       +2

Impacted Files	Coverage Δ
src/view/components/StyleDeclaration.vue	100% <ø> (ø)	⬆️
src/view/components/VueNode.vue	62.71% <ø> (ø)	⬆️
src/view/ui-logic/rendering.ts	98.74% <100%> (ø)
src/view/components/VueComponent.vue	91.3% <100%> (ø)	⬆️
src/view/components/VueSlot.vue	100% <100%> (ø)	⬆️
src/view/components/StyleValue.vue	43.85% <13.51%> (-56.15%)	⬇️
src/view/ui-logic/editing.ts	76.92% <76.92%> (ø)
src/view/ui-logic/style-value-lexer.ts	94.5% <94.5%> (ø)

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