types: refactor interfaces

[atomiks]

• Removes [key: string]: any from Props (see Typing problem with new native props + plugins #631)
• Makes all interfaces that use Props become generic (to use TProps)
• Add included plugins to Props so typechecking is enabled by default even if the plugin isn't passed (there is a DEV warning for this)

[atomiks]

Also added: function overloading types so TS knows the return value based on the targets argument:

tippy('button') // Instance[];
tippy(document.body) // Instance;

delegate('button', {target: 'string'}) // Instance[];
delegate(document.body, {target: 'string'}) // Instance;

[atomiks]

I think we should just add all the plugin types to Props itself 🤷‍♂

For custom plugins, the user does something like:

src/tippy.ts

import tippy, {Tippy, Props, Plugin} from 'tippy.js';

interface ExtendedProps extends Props {
  customX: boolean;
  customY: number;
}

export const customX: Plugin<ExtendedProps> = {
  name: 'customX',
  defaultValue: false,
  fn: () => ({}),
};

export const customY: Plugin<ExtendedProps> = {
  name: 'customY',
  defaultValue: 0,
  fn: () => ({}),
};

export default tippy as Tippy<ExtendedProps>;

src/index.ts

import tippy from './tippy';

// Both overloading and typechecking for custom plugins work
// DEV warning that `customX` and `customY` plugins were not passed
const [i] = tippy('button', {
  customX: true, 
  customY: 1000
});

i.setProps({customX: false});

// Also included plugins become part of `Props` itself
i.setProps({followCursor: true}); // DEV warning that they didn't pass the plugin

This is the simplest usage I think.

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That said it doesn't solve #631. There will be a type error if their plugin name conflicts with a newly introduced native one. There will be a DEV warning if this happens so they'll need to update the name to something else (or remove it). I expect this to be rare enough to not really be an issue, anyway.

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I also noticed that adding the overload doesn't isolate the red squiggly type error line to a single prop, the whole thing becomes squiggly making it harder to track down the violating prop. I'm not sure if that's just the way TS is though.