chore: rename ContainsItem to SliceContains (and add NotSliceContains)

feat: expose Diff() function

feat: add HasSuffix and HasPrefix

I am manually doing this  a lot in a very janky way: `assert.True(t,
strings.HasPrefix(...))`

fix: remove "No newline..."

feat: add IgnoreGoStringer()

feat: use %+v for displaying errors

Some error tracing libraries use this to write the full trace, which is
useful when debugging.

chore: bump repr to 0.4.0

feat: add OmitEmpty() compare option

fix: panic if message format arg is not a string

feat: support excluding types from comparison

This is supported by extending the `msgAndArgs...any` variadic parameter
to `msgArgsAndCompareOptions...any`. Any argument that is an
`assert.CompareOption` will be passed to `assert.Compare`.

eg.

```go
assert.Equal(t, a, b, "Unequal! %#v != %#v", a, b, assert.Exclude[time.Time]())
```