Add readme for theatric (#385)

* Add readme for theatric

* Add TOC for API

packages/theatric/README.md

@@ -0,0 +1,165 @@
+An easy to use Tweakpane/Leva-like library for React, built on top of
+Theatre.js.
+
+You can use Theatric to quickly tweak values in your React components, or create
+quick prototypes without worrying about setting up a UI.
+
+Unlike Leva or Tweakpane, Theatric can save or export the state of your controls
+and load it back in later. You can even share the state with other people, so
+they can see the same values you're seeing, or leave Theatric's `useControls`
+hooks in production, and let Theatric set the values from the provided state
+without displaying the UI.
+
+Since Theatric is built on top of Theatre.js, you can also animate all the
+values.
+
+It comes with no peer-dependencies, all you need to do to set it up is run
+`yarn add theatric` or `npm install theatric`.
+
+## API
+
+[`useControls(controls, options?)`](#usecontrolscontrols-options)
+
+[`initialize(config)`](#initializeconfig)
+
+[`types`](#types)
+
+### `useControls(controls, options?)`
+
+`useControls` is Theatric's main API. It is a React hook which you can call from
+anywhere in your component tree. It takes an object of controls and returns an
+object of values.
+
+```tsx
+import {useControls} from 'theatric'
+
+function Introduction() {
+  const {name, age} = useControls({name: 'Andrew', age: 28})
+
+  return (
+    <div>
+      Hey, I'm {name} and I'm {age} years old.
+    </div>
+  )
+}
+```
+
+Optionally, you can also provide a folder option in the options argument, which
+will namespace your controls to that folder in the UI. This is useful if you
+have multiple instances of the same component, in which case the controls would
+collide.
+
+```tsx
+import {useControls} from 'theatric'
+
+function Introduction({id}) {
+  const {name, age} = useControls({name: 'Andrew', age: 28}, {folder: id})
+
+  return (
+    <div>
+      Hey, I'm {name} and I'm {age} years old.
+    </div>
+  )
+}
+```
+
+`useControls` also returns two special properties, `$get` and `$set`, which you
+can use to get and set the values of your controls imperatively.
+
+```tsx
+import {useControls} from 'theatric'
+
+function Introduction() {
+  const {name, age, $get, $set} = useControls({name: 'Andrew', age: 28})
+
+  const increaseAge = useCallback(() => {
+    $set((values) => values.age, $get(age + 1))
+  }, [$get, $set])
+
+  return (
+    <div>
+      <div>
+        Hey, I'm {name} and I'm {age} years old.
+      </div>
+      <button onClick={increaseAge}>Increase age</button>
+    </div>
+  )
+}
+```
+
+You can also place buttons on the control panel to trigger actions. You can
+combine this with the `$get` and `$set` methods to create a more convenient UI.
+
+```tsx
+import {useControls, button} from 'theatric'
+
+function Introduction() {
+  const {name, age, $get, $set} = useControls({
+    name: 'Andrew',
+    age: 28,
+    IncrementAge: button(() => {
+      $set((values) => values.age, $get((values) => values.age) + 1)
+    }),
+  })
+
+  return (
+    <div>
+      <div>
+        Hey, I'm {name} and I'm {age} years old.
+      </div>
+    </div>
+  )
+}
+```
+
+### `initialize(config)`
+
+Optionally, you can call `initialize()` to initialize the UI with a certain
+state, or to take advantage of features like
+[assets](/docs/latest/manual/assets) support. `initialize()` takes the same
+config object as [`getProject`](/docs/latest/api/core#getproject_id-config_).
+
+```tsx
+import {initialize, useControls} from 'theatric'
+import theatricState from './theatricState.json'
+
+initialize({
+  state: theatricState,
+  assets: {
+    // Defaults to '/'
+    baseUrl: '/theatric-assets',
+  },
+})
+```
+
+### `types`
+
+The `types` export lets you provide more advanced options for your controls.
+
+For example, to specify a range for a number, or adjust the scrubbing
+sensitivity, you can use the `number` type.
+
+```tsx
+import {useControls, types} from 'theatric'
+
+function Introduction() {
+  const {name, age} = useControls({
+    name: 'Andrew',
+    age: types.number(28, {
+      // The range allowed in the UI (just a visual guide, not a validation rule)
+      range: [0, 10],
+      // Factor influencing the mouse-sensitivity when scrubbing the input
+      nudgeMultiplier: 0.1,
+    }),
+  })
+
+  return (
+    <div>
+      Hey, I'm {name} and I'm {age} years old.
+    </div>
+  )
+}
+```
+
+To learn more about types, check out the
+[types documentation](/docs/latest/api/core#prop-types).