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

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

vue/editor/playground/src/Toolbar.vue

@@ -0,0 +1,34 @@
+<script setup lang="ts">
+import { computed, onBeforeUnmount, ref } from 'vue';
+import type { Editor } from '@editor';
+import { isBlockActive, isMarkActive, setBlockType, toggleBlockType, toggleMark } from '@editor';
+
+const { editor } = defineProps<{ editor: Editor }>();
+
+// Re-evaluate active-states on every transaction.
+const rev = ref(0);
+const bump = (): void => void (rev.value += 1);
+editor.on('transaction', bump);
+onBeforeUnmount(() => editor.off('transaction', bump));
+
+const boldActive = computed(() => (rev.value, isMarkActive(editor.state, 'bold')));
+const italicActive = computed(() => (rev.value, isMarkActive(editor.state, 'italic')));
+const h1Active = computed(() => (rev.value, isBlockActive(editor.state, 'heading', { level: 1 })));
+const h2Active = computed(() => (rev.value, isBlockActive(editor.state, 'heading', { level: 2 })));
+const canUndo = computed(() => (rev.value, editor.canUndo()));
+const canRedo = computed(() => (rev.value, editor.canRedo()));
+</script>
+
+<template>
+  <div class="toolbar">
+    <button :data-active="boldActive || undefined" @mousedown.prevent="editor.command(toggleMark('bold'))"><b>B</b></button>
+    <button :data-active="italicActive || undefined" @mousedown.prevent="editor.command(toggleMark('italic'))"><i>I</i></button>
+    <span class="sep" />
+    <button :data-active="h1Active || undefined" @mousedown.prevent="editor.command(toggleBlockType('heading', { level: 1 }))">H1</button>
+    <button :data-active="h2Active || undefined" @mousedown.prevent="editor.command(toggleBlockType('heading', { level: 2 }))">H2</button>
+    <button @mousedown.prevent="editor.command(setBlockType('paragraph'))">P</button>
+    <span class="sep" />
+    <button :disabled="!canUndo" @mousedown.prevent="editor.undo()">Undo</button>
+    <button :disabled="!canRedo" @mousedown.prevent="editor.redo()">Redo</button>
+  </div>
+</template>