refactor(tiptap-extensions): Do not import the full lowlight library.

BREAKING CHANGE: `CodeBlockHighlight` was importing the full `lowlight` libraries, including _all_
syntax highlightning definitions from `highlight.js`. The new behavior changes the signature of
`CodeBlockHighlight` to accept an object with all syntax highlightning definitions. This means that
now the user of the library __MUST__ import languages themselves and tiptap will no longer
bundle the full `highlight.js` in itself.

packages/tiptap-extensions/src/nodes/CodeBlockHighlight.js

@@ -2,7 +2,7 @@ import { Node, Plugin } from 'tiptap'
 import { Decoration, DecorationSet } from 'prosemirror-view'
 import { toggleBlockType, setBlockType, textblockTypeInputRule } from 'tiptap-commands'
 import { findBlockNodes } from 'prosemirror-utils'
-import low from 'lowlight'
+import low from 'lowlight/lib/core'
 
 function getDecorations(doc) {
 	const decorations = []
@@ -12,7 +12,7 @@ function getDecorations(doc) {
 
 	const flatten = list => list.reduce(
 		(a, b) => a.concat(Array.isArray(b) ? flatten(b) : b), [],
-	)
+    )
 
 	function parseNodes(nodes, className = []) {
 		return nodes.map(node => {
@@ -63,6 +63,24 @@ function getDecorations(doc) {
 
 export default class CodeBlockHighlightNode extends Node {
 
+    constructor(options = {}) {
+        super(options)
+        try {
+            Object.entries(this.options.languages).forEach(entry => {
+                const [name, mapping] = entry
+                low.registerLanguage(name, mapping)
+            })
+        } catch (err) {
+            throw new Error('Invalid syntax highlight definitions: define at least one highlight.js language mapping')
+        }
+    }
+
+    get defaultOptions() {
+        return {
+            languages: {},
+        }
+    }
+
 	get name() {
 		return 'code_block'
 	}