Implement JsonText

[7hong13]

What this PR does / why we need it?

Implement JsonText.

Any background context you want to provide?

I removed createRange() function in JS-SDK version since it seems unnecessary.

What are the relevant tickets?

Fixes #

Checklist

• Added relevant tests or not required
• Didn't break anything

[codecov]

Codecov Report

Merging #66 (93338df) into main (e3fe2ca) will increase coverage by 2.08%.
The diff coverage is 87.83%.

@@            Coverage Diff             @@
##             main      #66      +/-   ##
==========================================
+ Coverage   78.94%   81.02%   +2.08%     
==========================================
  Files          51       52       +1     
  Lines        2289     2345      +56     
  Branches      334      335       +1     
==========================================
+ Hits         1807     1900      +93     
+ Misses        296      257      -39     
- Partials      186      188       +2     

Impacted Files	Coverage Δ
...in/kotlin/dev/yorkie/document/crdt/RgaTreeSplit.kt	65.88% <0.00%> (+3.92%)	⬆️
...ain/kotlin/dev/yorkie/document/json/JsonCounter.kt	93.33% <ø> (ø)
...c/main/kotlin/dev/yorkie/document/json/JsonText.kt	84.31% <84.31%> (ø)
...c/main/kotlin/dev/yorkie/api/OperationConverter.kt	100.00% <100.00%> (ø)
...kotlin/dev/yorkie/document/change/ChangeContext.kt	95.00% <100.00%> (+0.55%)	⬆️
...c/main/kotlin/dev/yorkie/document/crdt/TextInfo.kt	92.59% <100.00%> (ø)
...ain/kotlin/dev/yorkie/document/json/JsonElement.kt	88.88% <100.00%> (+13.88%)	⬆️
...main/kotlin/dev/yorkie/document/json/JsonObject.kt	91.89% <100.00%> (+0.34%)	⬆️
...lin/dev/yorkie/document/operation/EditOperation.kt	75.00% <100.00%> (+35.00%)	⬆️
yorkie/src/main/kotlin/dev/yorkie/core/Client.kt	84.81% <0.00%> (+0.42%)	⬆️
... and 6 more

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[hackerwins]

Thanks for your contribution.