docs: use PascalCase for file name (#350)

apps/documentation/src/components/ThemeBtn/ThemeBtn.tsx

@@ -0,0 +1,31 @@
+import type { JSX } from 'react'
+import {
+  ActionIcon,
+  useMantineColorScheme,
+  useComputedColorScheme,
+} from '@mantine/core'
+import { IconSun, IconMoon } from '@tabler/icons-react'
+import cx from 'clsx'
+
+import classes from './ThemeBtn.module.css'
+
+export default function ThemeBtn(): JSX.Element {
+  const { setColorScheme } = useMantineColorScheme()
+  const computedColorScheme = useComputedColorScheme('light', {
+    getInitialValueInEffect: true,
+  })
+
+  return (
+    <ActionIcon
+      onClick={() => {
+        setColorScheme(computedColorScheme === 'light' ? 'dark' : 'light')
+      }}
+      variant="default"
+      size="lg"
+      aria-label="Toggle color scheme"
+    >
+      <IconSun className={cx(classes.icon, classes.light)} stroke={1.5} />
+      <IconMoon className={cx(classes.icon, classes.dark)} stroke={1.5} />
+    </ActionIcon>
+  )
+}