docs: fix 8.3 typo and adding PHP version strategy (ddev#6721) [skip ci]

Co-authored-by: Stanislav Zhuk <[email protected]>
Co-authored-by: Randy Fay <[email protected]>

docs/content/users/extend/customization-extendibility.md

@@ -81,7 +81,7 @@ export PATH=$PATH:/var/www/html/somewhereelse/vendor/bin
 
 ## Changing PHP Version
 
-The project's `.ddev/config.yaml` file defines the PHP version to use. The [`php_version`](../configuration/config.md#php_version) can be changed to `5.6`, `7.0`, `7.1`, `7.2`,  `7.3`, `7.4`, `8.0`, `8.1`, `8.2`, '8.3', or `8.4`.
+The project's `.ddev/config.yaml` file defines the PHP version to use. The [`php_version`](../configuration/config.md#php_version) can be `5.6` through `8.4`, and new versions are added when they are released by the PHP Foundation.
 
 ### Older Versions of PHP