feat: adding gemini support

[darshit-s3]

Description

Introduces Gemini instrumentation for Typescript SDK by adding support for following methods:

• generateContent
• generateContentStream

Release https://github.com/Scale3-Labs/langtrace-trace-attributes/pull/85 before merging this PR

Checklist for adding new integration:

• [ ] Defined APIS in constants folder.
• [ ] Updated SERVICE_PROVIDERS in common.ts
• [ ] Created a folder under instrumentation with the name of the integration with atleast patch.ts and instrumentation.ts files.
• [ ] Added instrumentation in allInstrumentations in init.ts and to the InstrumentationType in types.ts files.
• [ ] Added examples for the new integration in the examples folder.
• [ ] Updated package.json to install new dependencies for devDependencies.
• [ ] Updated the README.md of langtrace-typescript-sdk to include the new integration in the supported integrations table.
• [ ] Updated the README.md of Langtrace's repository to include the new integration in the supported integrations table.
• [ ] Added new integration page to supported integrations in Langtrace Docs