Add lazy loading attribute to images as needed

[KevinBatdorf]

Fixes

Fixes #126

Description

Adds the loading="lazy" attribute to the image and falls back to loading="eager" if the user is below WP 5.5 (where the feature was introduced), or if the user disabled lazy loading.

My text editor auto adjusted some spacing. I left them in because they seemed reasonable enough.

I updated the readme and added my WP name as a contributor, but feel free to remove that if it's not appropriate!

Let me know if I missed something. I don't have a full understanding of the code base, so I may have overlooked something.

Tests

1. Add a CC license image (from footer, or block).
2. Check the image attribute

To disable:

1. Downgrade WP. If using CLI, the following should work. The --path is optional depending on your setup.

wp core update --path="htdocs/cms" --version="5.4" --force

2. Add a filter to functions.php or as a mu-plugin

add_filter('wp_lazy_loading_enabled', '__return_false');

Screenshots

Checklist

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the default branch of the repository (main or master).
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no
  visible errors.

Developer Certificate of Origin

Developer Certificate of Origin

Developer Certificate of Origin
Version 1.1

Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
1 Letterman Drive
Suite D4700
San Francisco, CA, 94129

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.


Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified
    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.

[hugosolar]

this is great. Thank you so much for your contribution