docs: minor fixes to main language reference page.

[aznashwan]

1. Normal comment - doc comment interleaving:

On 0.16.0-dev.1301+cbfa87cbe, the following definition produces the following docs:

/// This is a check if normal comments are interleaved with doc comments.
// Normal comment 1.
/// Doc comment 2.
// Normal comment 2.
/// Doc comment 3.
// Normal comment 3.
pub const Test = struct {
    test_field: u32,
};

$ zig build-lib -femit-docs src/root.zig
$ python3 -m http.server -b 127.0.0.1 8000 -d ./docs

2. Error name change:

As a new Zig learner, one of the most unexpected things I encountered was that you could just define a global error set value by just going error.AnyRandomName without having to import anything (e.g. const error = @import("error");) or pre-declare it in any other place (const AnyRandomName = 123;).

IMHO, such an early example in the reference page should not add an extra potential layer of confusion by making it clear that the error name does not need to be pre-imported and can be arbitrarily defined on the spot.

I'm open to a better name suggestion but it should IMHO not be any error name you'd expect to find in the stdlib.

[castholm]

I take the old comment to mean that ignoring normal comments was always the intended behavior and that the old autodoc implementation was wrong, so "currently" can probably be removed (as it misleadingly implies that the behavior is subject to change). A few lines above it is already mentioned that normal comments are ignored and that only the two types of doc comments are used for package documentation, so the entire paragraph can probably be reduced to just:

Doc comments can be interleaved with normal comments, which are ignored.

[aznashwan]

so the entire paragraph can probably be reduced

Great call, just updated it, thank you for the clarification!