feat($core): adds support for tension, beta, alpha in curves

[t-mullen]

Adds support for D3 curve modification methods like tension, alpha and
beta. Re-done because of the broken Git forks.

Closes #39

Updates

• Adds in support for all D3 curve modifying methods (.tension(), .alpha(), .beta(), any any other similar methods).

Demo screenshot or recording

The demo curveNatural has been replaced with the curveCardinal with a modified tension (it is visually identical.)

Review checklist (for reviewers only)

• Demos all features
• Documented/annotated
• Matches UI/UX specs
• Meets the code style guide
• Accessible
• Mobile first (responsive)
• RTL support (bidirectional text)
• Performant (limited bloat)

[t-mullen]

The idea to support the dual curve option instead of of two options gets pretty weird with the typings. I'm not sure if it's the best call.

[netlify]

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[theiliad]

I think we need to have a discussion here.

There are 2 ways to do this:
1.

@t-mullen @zvonimirfras @cal-smith which approach looks more ideal to you?

Aside from that the implementation works great, although I would suggest we throw a console.error when user enters curve options that don't exist.

[cal-smith]

I think 2 overall ... it's a little more complex, but it does a better job of keeping everything localized.

That said, does the rest of the library use x + xOptions? Or would the plan be to refactor any of those instances to the second style as well?

[theiliad]

@cal-smith I agree about approach number 2. Nope, usually we don't do x + xOptions.

[theiliad]

Any updates here @t-mullen?

[t-mullen]

The decided-upon API has been implemented.

[theiliad]

Looks good to me!

[theiliad]

@zvonimirfras @cal-smith ready to merge