comark/diff/missing-file · Name the file a ::diff changes

A diff is read by the file it changes, the way a review names a suggestion. Name it on the first block, like ```ts [src/ducks.ts], or with file.

Incorrect

::diff
```ts
const meals = 1
```
```ts
const meals = 2
```
::

lint-comark example.mdexample.md:1:1 comark/diff/missing-filediff: name the file in the first block (```ts [src/a.ts]) or with file="src/a.ts".Change the block as the message says.✖ 1 problem

Correct

::diff
```ts [src/ducks.ts]
const meals = 1
```
```ts
const meals = 2
```
::

lint-comark example.md✔ No problems