New free asset: Converter For Unity Splines

[_Aka_]

This converter is great, and has solidified my decision to make Curvy my primary spline app, since it acts as a bridge to other tools that use unity splines.

If I could ask for one update, it would be to update any existing curvy conversion instead of destroying it.
When it's destroyed, we lose all events and references to the spline, including from generators, and have to either manually re-assign everything or write a hacky automator as a workaround.

Edit: Noticed an issue:
Converter prevents builds due to editor code in non-editor folder (RequestProcessor.cs)

This is now fixed in the 1.3.0 update. Here is the full release notes:

## [1.3.0] - 2024-07-19
### Changed
- Unity To Curvy conversions now reuse existing Curvy Splines.
- Updated warning message when converting a Catmull-Rom spline
### Fixed
- Builds fail because of Converter.
- Updating a Unity Spline can lead to conversion even if conversion direction is Curvy To Unity.