Update Hugo to version 0.56.3

This is a bug-fix release with a couple of important fixes. After getting feedback about the new Hugo Modules feature, this release also adds some minor improvements:

It adds support for overlapping file mounts, even for the filesystems where we walk down the directory structure. One relevant example that is fixed by this release:

[module]
[[module.mounts]]
source="content1"
target="content"
[[module.mounts]]
source="content2"
target="content/docs"

The above is obviously both common and very useful. This was never an issue with the situations where load a specific file/directory (e.g. resources.Get "a/b/c/d/sunset.jpg").

User feedback also told us that these file mounts were a little hard to debug, so we added a new command that prints the configured mounts as a JSON:

hugo config mounts