Add the unit, display_decimal_places, and step parameter widget macro attributes

[Ripper53]

• unit macro for a unit suffix, eg. "°" or " px"
• display_decimal_places to show certain amount of decimal places for float numbers (default 2)
• step for little arrows on each end of a number input to increment and decrement based on the step value (default 1.)

Example Usage

Code:

#[unit(" MEOW")]
#[display_decimal_places(4)]
#[step(2.)]
meow_num: f64

Expected result shown in image after adjusting value to 2.51231237:

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Macros are not being used anywhere except in the copy_to_points function inside of vector_nodes.rs, however, these were already being used before and I believe they were not doing anything because a unit macro did not exist. The Multiplier field already added a unit suffix of "x" so the unit macro does not provide any utility, though, I have left it unchanged.

The way I tested to make sure these macros work:

1. Add a f64 field to the repeat function in vector_nodes.rs with the new macros
2. Compile code and in Graphite, add a Repeat node to a shape
3. See if the new field within the Repeat node changes depending on the parameters of the new macros