Type definitions for a Mithril-ui-form plugin

Mithril-ui-form is a declarative framwork to create forms using the front-end Mithril framework and mithril-materialized components using the materialize-css design theme.

There were two main reasons to convert the existing mithril-ui-form to a framework supporting plugins:

- The Leaflet map component was included by default, and you needed to import them even when not using a map. Recent versions (v1.0.0+) have removed support for the leaflet map component, so you need to include it manually yourself

``ts
import { leafletPlugin } from 'mithril-ui-form-leaflet-plugin';

...

registerPlugin('map', leafletPlugin);
`

- You could not add your own types, e.g. to create a questionnaire, I needed a (no-star-based) rating component, and that was not easy to integrate into a form. Now, you can just register it yourself.

`ts
registerPlugin('rating', myRatingPlugin, myReadonlyRatingPlugin);
`

Since each plugin is a Mithril FactoryComponent, i.e. a function that returns a Component object with a view method, it is very easy to roll your own.

`ts
import { FactoryComponent } from 'mithril';

export type PluginType = FactoryComponent<{
/* Initial value, typically a string, number or boolean /
iv: any;
/* Original properties of the form field /
field: Record;
/* Partially converted properties, e.g. the ones containing placeholders for other variables, e.g. label, description, etc. /
props: Record;
/* Label, raw version of props.label /
label?: string;
/* Only present when component is not readonly /
onchange?: (value: string | number | Array> | Date | boolean) => Promise;
}>;
``