Resolve "Expression-able if-statement"

Description

Implementing the expresion-able if-statement. Also adding some issue templates for Gitlab.

Checklist

Before you create this MR confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]). This will ensure a smooth and quick review process.

• I read the Contributor Guide and followed the process outlined there for submitting MRs.
• My MR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The flutter analyzer (flutter analyze) does not report any problems on my MR.
• I read and followed the Flutter Style Guide.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy. And afterwards run flutter pub get, which will update the pubspec.lock with the correct new version.
• I updated CHANGELOG.md to add a description of the change.
• I am willing to follow-up on review comments in a timely manner.
• I am done with this MR and removed the Draft status, by clicking on the Mark as ready button in this MR

Breaking Change

Does your MR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate a breaking change in CHANGELOG.md and increment major revision).
• No, this is not a breaking change.

Related Issues

Replace this paragraph with a list of issues related to this MR from the issue database. Indicate, which of these issues are resolved or fixed by this MR. If you created the MR within this project, this will be filled automatically

Closes #1 (closed)