プレビューの表示状態を記憶するように

[anatawa12]

What

Closes #11254

Why

記憶するでも毎回クリックしないといけない煩雑さからは開放されるのでこちらで良さそうだと思ったため。

Additional info (optional)

Checklist

• Read the contribution guide
• Test working in a local environment
• (If needed) Add story of storybook
• (If needed) Update CHANGELOG.md
• (If possible) Add tests

[codecov]

Codecov Report

Merging #11346 (6af9a00) into develop (007ed5c) will increase coverage by 0.02%.
Report is 58 commits behind head on develop.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop   #11346      +/-   ##
===========================================
+ Coverage    78.75%   78.77%   +0.02%     
===========================================
  Files          920      174     -746     
  Lines        97822    22745   -75077     
  Branches      7837      520    -7317     
===========================================
- Hits         77037    17918   -59119     
+ Misses       20785     4827   -15958     

Files Changed	Coverage Δ
packages/frontend/src/components/MkPostForm.vue	100.00% <100.00%> (ø)

... and 764 files with indirect coverage changes

[syuilo]

👍