Fix grammatical issues from Korean translation

[stevejkang]

I recently found out that a Korean translation of wtfjs was created, and it was harder to read than I thought, as it was written by a non-native speaker, and the 'translation tone' seemed to remain. Therefore, I tried to make the translation easier to read by enhancing the translation a little bit more.

The major changes are as follows.

• When 'postposition'(like 은/는/이/가/을/를) is placed behind English words or English words wrapped in backticks, unnecessary spaces are removed.
• It is the same word, but the parts used differently depending on the location are modified.
• There were many problems with spacing, so they were corrected.
• The sentence ends awkwardly modified.
• Other grammatically correct typos or errors.

[stevejkang]

Could you review this PR? @denysdovhan

[github-actions[bot]]

:tada: This PR is included in version 1.21.2 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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