Better snapshot formating

[Akiyamka]

Current snapshot md file contain json that look like plain text.
It can be much more readable with ```js around snap content.

Current	Can be

[novemberborn]

The output isn't strictly JavaScript though, for example this is how a buffer is snapshotted:

Buffer @Uint8Array [
  68656c6c 6f
]

[novemberborn]

Which happens to look OK enough in GitHub, but I'm not sure what other syntax bits the syntax highlighter may get weird about:

    Buffer @Uint8Array [
      68656c6c 6f
    ]

[RandomByte]

Maybe the syntax (e.g. "js") could be provided in the t.snapshot() call?

This would make snapshots (especially of JS) a lot more readable. We have a project where we generate JavaScript and syntax errors can happen. With some basic syntax highlighting in markdown you can spot this a lot easier.

[novemberborn]

@RandomByte are you snapshotting strings? They'll still be printed slightly differently in the Markdown.

The only way I see this working is a "raw" mode where the Markdown contains the string as-is, and then it would make sense to also provide a syntax tag.

[RandomByte]

@novemberborn Yes exactly. Strings of JavaScript code.

I guess you mean the backticks enclosing the string? They would indeed cancel out any JavaScript syntax highlighting, since the string simply becomes... a string in JavaScript.

Currently I get something like this:

> Snapshot 1

    `console.log("Hello World");
    `

My Expectation after somehow providing js syntax:

> Snapshot 1

    ```js
    console.log("Hello World");

    ```

Could this "raw" mode automatically engage if the developer provides a syntax tag?

[novemberborn]

Maybe an overload in SnapshotAssertion:

ava/types/assertions.d.cts

Lines 320 to 332 in a6f42ea

	export type SnapshotAssertion = {
	/**
	* Assert that `expected` is [deeply equal](https://github.com/concordancejs/concordance#comparison-details) to a
	* previously recorded [snapshot](https://github.com/concordancejs/concordance#serialization-details), or if
	* necessary record a new snapshot.
	*
	* Returns `true` if the assertion passed and throws otherwise.
	*/
	(expected: any, message?: string): true;
	/** Skip this assertion. */
	skip(expected: any, message?: string): void;
	};

)

snapshot(expected: string, options?: { formatAsCodeBlock: true | string }, message?: string)

This options object should only be accepted for string values, and must only contain formatAsCodeBlock. string values would be the syntax, and true would be the same as an empty string (but less weird).

When formatting, backticks would need to be escaped properly.