Bump recommended hex version to v6.0

Bump version to 5.3.1

Update macos-13 based runner to macos-15

Bump version to 5.2.0 and update changelog

Bump version to 5.1.1 and update Changelog

Provide a LocalIncludeLoader struct for the 'include_loader' option

Instead of passing a 'include_loader' and a separate
'locale_loader_path' option the Mjml.to_html/2 a
Mjml.ParserOptions.LocalIncludeLoader struct is provided to be able to
pass the related configs in one value.

The LocalIncludeLoader has a path field (optional) that can be used to
define a custom include base path.

This approach allows us to provide other include loaders that are
already implemented in mrml in the future without the need to add more
option keys.

The explicite Noop include loader is dropped from the Elixir side,
because it can just be used as the default on the Rust side if no other
valid include loader option was provided.

Invalid include loader options are checked on the Elixir side now
instead of panicking on the Rust side (which also fixes the issue with
the panick message logging in successful test runs).

Use macos-13 runner for GitHub actions

See actions/runner-images#10721 for the
deprecation notice.

Update Changelog + Readme for v4.0.0

Merge pull request #143 from adoptoposs/dependabot/cargo/native/mjml_…

…nif/mrml-3.1.5

Bump mrml from 3.0.4 to 3.1.5 in /native/mjml_nif

Update changelog for v3.0.3