[Coffee Maker Example App] Simulate polling for fetching coffee orders

[ulusoyca]

Description

This PR prepares the coffee maker navigator 2.0 demo app for the workshop which will be held in Flutter&Friends.

Changes:

• Simulate polling with 3 seconds interval for the fetching of the coffee orders.

[github-actions]

It appears that this PR does not include any tests. It is recommended to add tests, especially for critical changes, to ensure code quality and prevent regressions. However, if this PR is only updating samples or documentation, feel free to skip adding tests and disregard this comment.

[ulusoyca]

It appears that this PR does not include any tests. It is recommended to add tests, especially for critical changes, to ensure code quality and prevent regressions. However, if this PR is only updating samples or documentation, feel free to skip adding tests and disregard this comment.

@TahaTesser Cool stuff!

[github-actions]

It appears that this PR does not include any tests. It is recommended to add tests, especially for critical changes, to ensure code quality and prevent regressions. However, if this PR is only updating samples or documentation, feel free to skip adding tests and disregard this comment.

[TahaTesser]

I'll probably remove synchronised condition so it doesn't repeat the comment when pushing new commits or rebasing the PR. Only comment when PR is opened or reopened.