docs: add guide to using value classes

[erie0210]

Please let me know which file I should add it to and I will move it. I'm trying to write a Korean document and translate it into English.

Motivation

• Add guide to how to use value class.

Modifications

Commit Convention Rule

• Please commit your modification based by conventional commit:

Commit type	Description
feat	New Feature
fix	Fix bug
docs	Documentation only changed
ci	Change CI configuration
refactor	Not a bug fix or add feature, just refactoring code
test	Add Test case or fix wrong test case
style	Only change the code style(ex. white-space, formatting)
chore	It refers to minor tasks such as library version upgrade, typo correction, etc.

• If you want to add some more commit type please describe it on the Pull Request

Result

• Please describe the result after this PR is merged.

Closes

• 559

[cj848]

You need to remove the .DS_Store files.

[erie0210]

Sure, why not including '.DS_Store' for .gitinore? @cj848

[shouwn]

Sure, why not including '.DS_Store' for .gitinore?

I guess I forgot to put it in.

[shouwn]

Please move the file to the FAQ folder.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.01%. Comparing base (95304dd) to head (0eb4a45). Report is 24 commits behind head on develop.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #707 +/- ## ======================================== Coverage 92.01% 92.01% ======================================== Files 335 335 Lines 3419 3419 Branches 203 203 ======================================== Hits 3146 3146 Misses 213 213 Partials 60 60 ```

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