Add gemini plugin to marketplace

[NickLewanowicz]

Submit a new Plugin to Marketplace

I forked the existing openai plugin and refactored it to instead use the gemini API. This is particularly useful cause the flash model has a context of 128k and is free up to 15 times a minute and ~1500/day so for most people it would be great for all their notes and if if you choose to use the pro model you can even go up to 1M tokens context.

Plugin Github repo URL: https://github.com/NickLewanowicz/logseq-plugin-gemini

Github releases checklist

• [x] a legal package.json file.
• [x] a valid CI workflow build action for Github releases. (theme plugin for this).
• [ ] a release which includes a release zip pkg from a successful build.
• [x] a clear README file, ideally with an image or gif showcase. (For more friendly to users, it is recommended to have English version description).
• [x] a license in the LICENSE file.