rule: Expressions can occur in text content or in attribute value positions.

would it be worth while (and, tractable) to have a rule that enforces the above lit-html constraint? the following concocted code, for example, causes an exception:
````
render(html`

`, $('body')[0])
````

while the following produces happiness
````
render(html`

`, $('body')[0])
````
(if that's what you were looking for.)

cheers.

該 issue 提議為 lit-html 新增一條新的 ESLint 規則，以強制表達式僅出現在文字內容或屬性值位置。先查看外掛中現有的規則實作，以瞭解 lit-html 範本的 AST 模式。查看表達式是如何被偵測與驗證的。透過檢查 lit-html 對表達式放置的限制來確定此規則的範圍。撰寫有效與無效案例的測試，然後在適當目錄中實作該規則。

由索引模型根據 Issue 內容生成。