Allow disabled list items in fields picker

app/src/components/v-field-template/field-list-item.vue

@@ -1,6 +1,7 @@
 <template>
 	<v-list-item
 		v-if="field.children === undefined"
+		:disabled="field.disabled"
 		@click="$emit('add', `${parent ? parent + '.' : ''}${field.field}`)"
 	>
 		<v-list-item-content>{{ field.name }}</v-list-item-content>

app/src/components/v-field-template/types.ts

@@ -3,5 +3,6 @@ import { TranslateResult } from 'vue-i18n';
 export type FieldTree = {
 	field: string;
 	name: string | TranslateResult;
+	disabled?: boolean;
 	children?: FieldTree[];
 };