feat: Added Base64 related utility functions

[klmhyeonwoo]

Description

• Base64로 인코딩 및 디코딩하는 유틸 함수가 추가되었어요!
• 기존 atob, btoa에서 유니코드와 더불어 한글까지 지원하는 형태예요

closes: #50
closes: #51

[Copilot]

Pull Request Overview

This PR adds Base64 encoding/decoding utilities and a type utility for plain object detection. It also improves the null property clearing function to handle edge cases better.

• Adds encodeBase64 and decodeBase64 functions with special character handling options
• Introduces isPlainObject utility to distinguish plain objects from arrays, dates, and custom objects
• Enhances clearNullProperties to properly handle arrays and nested objects using the new plain object check

Reviewed Changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
package/commonUtil/encodeBase64/index.ts	Implements Base64 encoding with URI encoding options
package/commonUtil/decodeBase64/index.ts	Implements Base64 decoding with URI decoding options
package/typeUtil/isPlainObject/index.ts	Adds utility to check for plain objects vs other object types
package/objectUtil/clearNullProperties/index.ts	Improves null property clearing with better object type detection
package/typeUtil/index.ts	Exports the new type utility with incorrect naming

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[klmhyeonwoo]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	80.06%	249 / 311
🔵	Statements	80.06%	249 / 311
🔵	Functions	96%	24 / 25
🔵	Branches	91.89%	102 / 111

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
package/commonUtil/decodeBase64/index.ts	80%	75%	100%	80%	14-15
package/commonUtil/encodeBase64/index.ts	80%	75%	100%	80%	14-15

Generated in workflow #76 for commit 0d51bb0 by the Vitest Coverage Report Action

[prgmr99]

고생하셨습니다~~!!