feat: add useLocalStorageMap for reactive localStorage management wit…

[aaronsuuu]

…h Map interface

This pull request introduces a new useLocalStorageMap composable to manage reactive Map objects synchronized with localStorage. The key changes include the implementation of the composable, documentation, a demo, and comprehensive test coverage.

Implementation of useLocalStorageMap:

• Added the useLocalStorageMap composable in index.ts, which provides a reactive Map interface backed by localStorage. It uses a custom serializer to handle the conversion between Map and JSON.

Documentation and Examples:

• Created index.md to document the useLocalStorageMap composable, including its usage, API, and example code snippets.
• Added a demo in demo.vue to showcase the functionality of useLocalStorageMap, including adding, deleting, and displaying key-value pairs.

Testing:

• Added unit tests in index.test.ts to ensure the correctness of useLocalStorageMap under various scenarios, such as basic usage, handling empty maps, non-string keys, complex objects as values, and options like listenToStorageChanges.

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

⚠️ Slowing down new functions

Warning: Slowing down new functions

As the VueUse audience continues to grow, we have been inundated with an overwhelming number of feature requests and pull requests. As a result, maintaining the project has become increasingly challenging and has stretched our capacity to its limits. As such, in the near future, we may need to slow down our acceptance of new features and prioritize the stability and quality of existing functions. Please note that new features for VueUse may not be accepted at this time. If you have any new ideas, we suggest that you first incorporate them into your own codebase, iterate on them to suit your needs, and assess their generalizability. If you strongly believe that your ideas are beneficial to the community, you may submit a pull request along with your use cases, and we would be happy to review and discuss them. Thank you for your understanding.

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