Fix extension buttons spacing, add extension example (#229)

* Fix extension buttons spacing & styles
* Refactor extension button styles
* Clean up extension prism

packages/playground/src/shared/hello-world-extension/App.tsx

@@ -0,0 +1,37 @@
+import {editable as e, SheetProvider} from '@theatre/r3f'
+import {Stars, TorusKnot} from '@react-three/drei'
+import {getProject} from '@theatre/core'
+import React from 'react'
+import {Canvas} from '@react-three/fiber'
+
+function App() {
+  return (
+    <div
+      onClick={() => {
+        // return setBgIndex((bgIndex) => (bgIndex + 1) % bgs.length)
+      }}
+      style={{
+        height: '100vh',
+      }}
+    >
+      <Canvas
+        dpr={[1.5, 2]}
+        linear
+        gl={{preserveDrawingBuffer: true}}
+        frameloop="demand"
+      >
+        <SheetProvider sheet={getProject('Space').sheet('Scene')}>
+          <ambientLight intensity={0.75} />
+          <e.group uniqueName="trefoil">
+            <TorusKnot scale={[1, 1, 1]} args={[1, 0.3, 128, 64]}>
+              <meshNormalMaterial />
+            </TorusKnot>
+          </e.group>
+          <Stars radius={500} depth={50} count={1000} factor={10} />
+        </SheetProvider>
+      </Canvas>
+    </div>
+  )
+}
+
+export default App

packages/playground/src/shared/hello-world-extension/index.tsx

@@ -0,0 +1,50 @@
+import React from 'react'
+import ReactDOM from 'react-dom'
+import App from './App'
+import type {ToolsetConfig} from '@theatre/studio'
+import studio from '@theatre/studio'
+import extension from '@theatre/r3f/dist/extension'
+import {Box, prism, Ticker, val} from '@theatre/dataverse'
+
+studio.extend(extension)
+studio.extend({
+  id: '@theatre/hello-world-extension',
+  toolbars: {
+    global(set, studio) {
+      const exampleBox = new Box('mobile')
+      return prism<ToolsetConfig>(() => [
+        {
+          type: 'Switch',
+          value: val(exampleBox.derivation),
+          onChange: (value) => exampleBox.set(value),
+          options: [
+            {
+              value: 'mobile',
+              label: 'view mobile version',
+              svgSource: '😀',
+            },
+            {
+              value: 'desktop',
+              label: 'view desktop version',
+              svgSource: '🪢',
+            },
+          ],
+        },
+        {
+          type: 'Icon',
+          title: 'Example Icon',
+          svgSource: '👁‍🗨',
+          onClick: () => {
+            console.log('hello')
+          },
+        },
+      ]).tapImmediate(Ticker.raf, (value) => {
+        set(value)
+      })
+    },
+  },
+  panes: [],
+})
+studio.initialize()
+
+ReactDOM.render(<App />, document.getElementById('root'))