Improvement of AssetServer::load documentation to help find a way to load from file with hash in filename

[bugsweeper]

Objective

• Fixes Asset Server incorrectly parsing files with # in their name #13192 .
• It is not possible to specify the path of the file and the subasset in it in one string slice, if there is a hash in the file name, because hash is separator between filename and subasset, so they must be separated explicitly

Solution

• Improved documentation for AssetServer::load.

[alice-i-cecile]

I like this feature but I feel pretty strongly that these should be constructor methods rather than From impls. They're easier to discover and much nicer to document: even just the method and argument names make things a lot less error prone.

[bugsweeper]

@alice-i-cecile I used From<(Path, label)> because AssetServer::load uses Into<AssetPath> in arguments. If you prefer constructor there is a way (more complex, but exists) for such thing:
asset_server.load(AssetPath::from_path(Path::new("A#.ron")).with_label("Scene0"));
I proposed simplier way:
asset_server.load((Path::new("A#.ron"), "Scene0"));
I agree that documenting should be done, I could add this way of loading into AssetServer::load doc-comment.
If this is bad idea we can close this PR and parent issue, because constructor way already exists.

[bugsweeper]

May be we should improve just AssetServer::load doc-comment with explicit path and label example

[alice-i-cecile]

May be we should improve just AssetServer::load doc-comment with explicit path and label example

Great idea :) That's definitely my preference.

[alice-i-cecile]

Looks great. Just remember to update the title and PR description!

[bugsweeper]

@alice-i-cecile Is there anything else I could do to move forward?