Documentation for default type of `E` in `IResult`

[HarrisonMc555]

If I'm not mistaken, the documentation for the default type of E for IResult for all 5.x and 6.x releases is inaccurate.

In releases 5.x, the documentation claims that the default type of E is u32. However, it appears that the actual default type of E is (I, nom::error::ErrorKind).

In releases 6.x (so far), the documentation claims that the default type of E is (I, nom::ErrorKind). However, it appears that the actual default type of E is nom::error::Error<I>.

I'm willing to submit a pull request to change this, but I have a few questions:

1. Are my conclusions correct? Is the documentation incorrect for both the 5.x and 6.x releases?
2. Should I submit a fix for the documentation for a previous release (i.e. 5.x)? If so, how do I go about doing so?
3. Should we backport the documentation updates to all previous releases? I.e. 6.0.0 and 6.0.1?