Add sample implementing compatibility with the pre 1.4 Reflex API

[octia]

Description

Added the Samples folder to the project, as well as the first sample.
The new sample adds compatibility with the old Reflex API. Importing the sample should allow projects using upgrading from pre-1.4 Reflex versions, to function without manually upgrading to the new API.

Fixes #132

Remarks

It should be considered whether the documentation should be updated to include information about the sample.
It should be considered whether the samples should be unit tested in any way.

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

Tests pass. I also tested the compatibility API with a project of mine which uses the old API.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have checked my code and corrected any misspellings
• I have checked that Reflex.GettingStarted still runs nicely