add vearch vectorstore

[zhanghexian]

PR Checklist

• [ ] Read the Contributing documentation.
• [ ] Read the Code of conduct documentation.
• [ ] Name your Pull Request title clearly, concisely, and prefixed with the name of the primarily affected package you changed according to Good commit messages (such as memory: add interfaces for X, Y or util: add whizzbang helpers).
• [ ] 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).
• [ ] Describes the source of new concepts.
• [ ] References existing implementations as appropriate.
• [ ] Contains test coverage for new functions.
• [ ] Passes all golangci-lint checks.

[zhanghexian]

Excuse me, when I submitted the code, I found that there was an error in the vectorstores/vectorstore.go(Option not defined), how should I modify it,thanks