Matchers isn't as typed as some users would like (see jestjs#13334, jestjs#13812).
For users who want to customize it by extending the `Matchers`
interface, it's useful to have access to the type of `actual` (the
argument of `expect`) so you can do, say,
```ts
interface Matchers<R, T> {
    toTypedEqual(expected: T): R
}
```
This commit exposes it. The first-party matchers still have the same
types as before.

Co-authored-by: Tom Mrazauskas <tom@mrazauskas.de>

Co-authored-by: Tom Mrazauskas <tom@mrazauskas.de>

Co-authored-by: Tom Mrazauskas <tom@mrazauskas.de>

Co-authored-by: Tom Mrazauskas <tom@mrazauskas.de>