Move utils back into main file

src/index.js

@@ -1,6 +1,5 @@
 import React from 'react'
 import PropTypes from 'prop-types'
-import { getIdFromTree } from './utils'
 
 const FootnotesContext = React.createContext({})
 
@@ -160,3 +159,29 @@ export const FootnotesProvider = ({ children, footnotesTitleId }) => {
 FootnotesProvider.defaultProps = {
   footnotesTitleId: 'footnotes-label',
 }
+
+function getTextFromTree(tree) {
+  let text = ''
+
+  if (typeof tree === 'string') {
+    text += tree
+  } else if (Array.isArray(tree)) {
+    text += tree.map(getTextFromTree).join('')
+  } else if (tree.props.children) {
+    text += getTextFromTree(tree.props.children)
+  }
+
+  return text
+}
+
+export function getIdFromTree(tree) {
+  return (
+    getTextFromTree(tree)
+      .toLowerCase()
+      // Remove any character that is not a letter, a number, an hyphen or an
+      // underscore, regardless of casing
+      .replace(/[^a-z0-9-_\s]/g, '')
+      // Replace all spaces with hyphens
+      .replace(/\s+/g, '-')
+  )
+}

src/test.js

@@ -1,6 +1,5 @@
 import React from 'react'
-import { Footnotes, FootnotesProvider, FootnoteRef } from './'
-import { getIdFromTree } from './utils'
+import { Footnotes, FootnotesProvider, FootnoteRef, getIdFromTree } from './'
 import { render, configure, screen } from '@testing-library/react'
 import '@testing-library/jest-dom/extend-expect'