fix(frontend): mfmFunctionPickerを使用して挿入する際のハンドリングを改善

[kakkokari-gtyih]

What

Why

Fix #17015

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

❌ Patch coverage is 0% with 27 lines in your changes missing coverage. Please review.
✅ Project coverage is 14.02%. Comparing base (cdb958c) to head (7894d50).
⚠️ Report is 5 commits behind head on develop.

Files with missing lines	Patch %	Lines
packages/frontend/src/components/MkPostForm.vue	0.00%	15 Missing and 5 partials ⚠️
...ckages/frontend/src/utility/mfm-function-picker.ts	0.00%	5 Missing and 1 partial ⚠️
packages/frontend/src/os.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #17018      +/-   ##
===========================================
- Coverage    14.03%   14.02%   -0.01%     
===========================================
  Files          238      238              
  Lines        11296    11302       +6     
  Branches      3736     3740       +4     
===========================================
  Hits          1585     1585              
- Misses        7586     7588       +2     
- Partials      2125     2129       +4     

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[kakkokari-gtyih]

lint通った

[kakkokari-gtyih]

コンフリクト解消

[kakkokari-gtyih]

コンフリクト解消

[kakkokari-gtyih]

👀