feat(editor): eslint/tsconfig migration + type fixes

@robonen/editor: migrate to eslint flat config + composite tsconfig; fix
convergence test type annotations.

vue/editor/src/marks/code.ts

@@ -0,0 +1,13 @@
+import { defineMark } from '../registry';
+
+export const code = defineMark({
+  type: 'code',
+  spec: {
+    inclusive: false,
+    rank: 9,
+    excludes: '_all', // inline code wins: it strips every other mark on the range
+    toDOM: () => ['code', 0],
+    parseDOM: [{ tag: 'code' }],
+  },
+  meta: { title: 'Inline code', icon: 'code', hotkey: 'Mod-e' },
+});