add automatic pull request gemini review

[GREENRAT-K405]

I have used gemini-2.5-flash.

Just create an api key in google ai studio and add it to secrets of github repo for concore-lite.

steps:

1. 
2. copy the api key
3. go to the setting of repository

4. go to secrets and variables -> actions

5. click on new repository secret

[GREENRAT-K405]

@pradeeban @Rahuljagwani, I tried other models too like the bot Ishaan used was 1.5-flash initially then 2.0-flash. But I was having too much trouble with them, like whenever I tried to review a PR, the github actions would respond with error like gemini_key_problem, model not available, this model doesn't aren't generative model, which definetly were completely misguiding errors.

I believe gemini-2.5-flash won't cause too much problem.
Also, I can share my API keys if you want to test it out quickly.

[GREENRAT-K405]

I will create a dummy PR after the changes are updated to check whether the review is working or not. If everything works fine, I will make the changes for other repos also.