fit: pagination start end month

[MarceloRab]

#Description

Added the feature to call back when reaching the first page and requesting a previous month and when reaching the last page and requesting a subsequent month.

Issue: #452

This was the best I could do. Adding a Gesturedetector only on the first and last month(pages). Because on the first and last page the PageView stops returning horizontal gesture listeners. This way I don't need to use NeverScrollableScrollPhysics to activate the gesture callback on the first and last page.

You can see from the commits that there has been an evolution. Bringing the final and initial drag return function only to the first and last pages. For there to be pagination, in addition to the gestures, the upper page change arrows need to remain on the first (left arrow) and last (right arrow). This work is up to the builder. In my app the arrows remain because I use [headerBuilder] manually.

This work took me a long time because I had to manipulate a PageView controller and GestureDetector. And this is my first fork with pull request.

I hope to contribute something.

• The title of my PR starts with a Conventional Commit prefix (fix:, feat:, docs: etc).

• [ ] I have followed the Contributor Guide when preparing my PR.

• [ ] I have updated/added tests for ALL new/updated/fixed functionality.

• I have updated/added relevant documentation in docs and added dartdoc comments with ///.

• [ ] I have updated/added relevant examples in examples or docs.

• [ ] Yes, this PR is a breaking change.

• No, this PR is not a breaking change.