README: add info about use of other projects

... as well as funding info.

Includes excluding one URL from the "dead URL" markdown check as it consistently refuses to validate, even though the URL is valid and correct.

Author: jrfnl

.remarkrc

@@ -8,7 +8,14 @@
     ["remark-lint-linebreak-style", "unix"],
     ["remark-lint-link-title-style", "\""],
     ["remark-lint-ordered-list-marker-style", "."],
-    "remark-lint-no-dead-urls",
+    [
+        "remark-lint-no-dead-urls",
+        {
+            "skipUrlPatterns": [
+                "^https://www\\.gnu\\.org/software/wget/"
+            ]
+        }
+    ],
     "remark-lint-no-duplicate-defined-urls",
     "remark-lint-no-duplicate-definitions",
     "remark-lint-no-empty-url",

README.md

@@ -169,12 +169,26 @@ Contributions to this project are welcome. Clone this repository, create a new b
 If unsure whether the changes you are proposing would be welcome, open an issue first to discuss your proposal.
 
 
+## Funding
+
+This project is part of the [PHPCSStandards Open Collective](https://opencollective.com/php_codesniffer) and financial support for this project is always appreciated!
+
+
 ## Copyright and License
 
-The phpcsstandards/xmllint-validate GitHub Action is ©copyright PHPCSStandards and contributors and licensed for use under the terms of the MIT License (MIT).
+The phpcsstandards/xmllint-validate GitHub Action is [©copyright PHPCSStandards and contributors](https://github.com/PHPCSStandards/xmllint-validate/graphs/contributors) and licensed for use under the terms of the MIT License (MIT).
 Please see [LICENSE](LICENSE) for more information.
 
 
+### Other Credits
+
+This action gratefully makes use of the following externally provided tools which are each governed by their own licensing:
+
+* [`xmllint](https://gnome.pages.gitlab.gnome.org/libxml2/xmllint.html)
+* [`xmllint-problem-matcher`](https://github.com/korelstar/xmllint-problem-matcher)
+* [`wget`](https://www.gnu.org/software/wget/)
+
+
 [Composer]:        https://getcomposer.org
 [PHPUnit]:         https://phpunit.de/index.html
 [PHP_CodeSniffer]: https://github.com/PHPCSStandards/PHP_CodeSniffer