Add specified easing functions specified in (#88)

[tmpr]

What was added

Functions for circular, sine, exponential and bouncing easing have been added to easing.rs. Further, I added 3 constants. This doesn't have to close (#88), since one could still add functions.

Remarks

• I took most functions from https://easings.net/, yet had no idea yet how to test the functions.
• A few things about the bouncing easing could be added improved:
  • One could clarify the choice of numbers
  • Some of the code could be more compact and more configurable.

[lukechu10]

Hi there. Thanks for taking the time to contribute to Maple! About testing the easing functions, I plan to add something similar to https://svelte.dev/examples#easing which should allow to visually test the easing functions. If I can get that finished fast enough, you can rebase it.

[lukechu10]

I thought about testing and a simple sanity test could just be checking that ease(0.0) == 0.0 and ease(1.0) == 1.0.

A macro could generate these test cases for all the easing functions.

[lukechu10]

I got a few nits if you don't mind. I would prefer if all the numbers had at least 1 digit after the decimal point (so 1.0 instead of 1.). I think this makes it easier to see that it's a float rather than a number with a function call. It might also be clearer if you used associated functions (so f32::powi(t - 1.0, 2) instead of (t - 1.0).powi(2)).

I tried out the easing functions in the tweened example (you can run it using trunk serve) and some of them didn't work as expected so I added some fixes.

[tmpr]

I switched out the formats now, but again this is just formalities so I hope you like it this way. :)

[lukechu10]

Looks good. I'll merge this now