Add phpmd3 task

[guvra]

Q	A
Branch	2.x
Bug fix?	yesn't (grumphp is not able to run phpmd with php 8.5)
New feature?	yes
BC breaks?	no (but will introduce a BC break in the future if phpmd3 replaces phpmd)
Deprecations?	no
Documented?	yes
Fixed tickets	#1209

This PR adds compatibility with the 3.x-dev branch of phpmd.

It looks like a bad idea to support a dev branch, but:

• This is the only branch compatible with php 8.5.
• The 2.x branch is not maintained anymore so it will never be compatible with php 8.5.
• The maintainers recommend to use this branch (cf. Missing release for the PHP 8.5 compatibility fix phpmd/phpmd#1280 (comment)).

For example, Magento 2.4.9 uses the 3.x-dev branch by default.

TODO

• Decide whether creating a task name phpmd3 is the best option
• Check unit tests (I didn't manage to run them locally on php 8.5)

New Task Checklist:

• Are the dependencies added to the composer.json suggestions?
• Is the doc/tasks.md file updated?
• Are the task parameters documented?
• Is the task registered in the tasks.yml file?
• Does the task contains phpunit tests?
• Is the configuration having logical allowed types?
• Does the task run in the correct context?
• Is the run() method readable?
• Is the run() method using the configuration correctly?
• Are all CI services returning green?