Adding dynamic_theme and gemini_tasks

[RedBrogdon]

Adds two new samples that use the Google Generative AI SDK for Dart. Both were created by @rodydavis. I'm merely the uploader so to speak.

Pre-launch Checklist

• I read the [Flutter Style Guide] recently, and have followed its advice.
• I signed the [CLA].
• I read the [Contributors Guide].
• I updated/added relevant documentation (doc comments with ///).
• All existing and new tests are passing.

[parlough]

I saw Rody uploaded these to the package repo too (dynamic theme, gemini tasks). Is this intended to supersede those?

[ericwindmill]

I saw Rody uploaded these to the package repo too (dynamic theme, gemini tasks). Is this intended to supersede those?

I believe there was a discussion in which folks were determining whether this repo was the more appropriate home for these samples. I'm guess they determined it was.

[RedBrogdon]

From what I understand, there was a discussion in which folks decided that this repo was the more appropriate home for these samples.

Bingo bango. The other PRs will be closed.