chore: add .env.example for easier environment setup and refine .gitignore

[piotrski]

I’ve made a couple of updates here to developer experience:

• Added .env.example for easier environment setup
  This provides a template for environment variables, helping developers get their local setup configured quickly.

• Updated .gitignore to exclude Azurite local storage files
  We’ve added patterns to ignore Azurite's local storage files (__azurite_db_*, __blobstorage__, __queuestorage__), keeping the working directory cleaner during local development.

[piotrski]

@microsoft-github-policy-service agree company="Callstack"

[lucen-ms]

Something is missing here.

[lucen-ms]

@piotrski will you be finishing the PR please?

[piotrski]

@lucen-ms apologies, it must have slipped my mind. I'll take a look at this later today.

[piotrski]

I've updated the formatting of the .env.example file to make it cleaner and more organized. Additionally, I've added information indicating which variables are required, as you requested.

Let me know if you have any feedback or if further adjustments are needed!

[lucen-ms]

AZURE_STORAGE_ACCOUNT=    # Storage account for testing (if TEST_AZURE_STORAGE=true)
AZURE_STORAGE_ACCESS_KEY= # Storage access key for testing

This is duplication of the same settings above which will override them. Every setting should be only once in the example.

[piotrski]

You're right, I just removed them.

[lucen-ms]

Thank you @piotrski for the contribution - I've merged your changes.