Display and set firstNode

[thierryc]

This pull request introduces two new features to enhance the plugin's functionality, particularly for vector export in font design and icon creation:

First Point Indicator: Adds a visual indicator to highlight the first point of a loop. This is crucial for variable font design and helps users easily identify the starting point of paths.
First Point Selection: Implements the ability to define the first point by clicking on another point in the path. This gives users more control over path orientation and starting positions.

Additional changes:

Updated the manifest file
Added tooling improvements

These features were developed to facilitate vector export for font design in the Glyph app and icon creation for SF symbols, where the first point's position is particularly important.