chore: Move editor into codebase (#2930)

shared/editor/marks/Highlight.ts

@@ -0,0 +1,45 @@
+import { toggleMark } from "prosemirror-commands";
+import { MarkSpec, MarkType } from "prosemirror-model";
+import markInputRule from "../lib/markInputRule";
+import markRule from "../rules/mark";
+import Mark from "./Mark";
+
+export default class Highlight extends Mark {
+  get name() {
+    return "highlight";
+  }
+
+  get schema(): MarkSpec {
+    return {
+      parseDOM: [{ tag: "mark" }],
+      toDOM: () => ["mark"],
+    };
+  }
+
+  inputRules({ type }: { type: MarkType }) {
+    return [markInputRule(/(?:==)([^=]+)(?:==)$/, type)];
+  }
+
+  keys({ type }: { type: MarkType }) {
+    return {
+      "Mod-Ctrl-h": toggleMark(type),
+    };
+  }
+
+  get rulePlugins() {
+    return [markRule({ delim: "==", mark: "highlight" })];
+  }
+
+  toMarkdown() {
+    return {
+      open: "==",
+      close: "==",
+      mixable: true,
+      expelEnclosingWhitespace: true,
+    };
+  }
+
+  parseMarkdown() {
+    return { mark: "highlight" };
+  }
+}