create xdoc documetation page to explain details of Xpath support

[romani]

We have a lot of Xpath details to share with users
so we need some page to put all that details in one place

To do:
create page under
https://checkstyle.org/config.html
with name "XPath" and put here all details and bunch of examples of xpath
links to CLI options, links to filters/checks.

Remove all links to master code from MatchXpath Check, detected at #8902 (comment)

related request for update - #6456

[nrmancuso]

From #142:

we need to create a searchable repository (conceptually, not necessarily a github repo) of MatchXPath modules with metadata tags and examples like this to help users easily discover such xpath modules.

[romani]

I Propose to use https://checkstyle.org/checks/coding/matchxpath.html#Examples as place for good examples that are like Checks, so user will find description and will see config and it will be checked by build to be actual.

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I just tested search of Google on our pages, https://www.google.com/search?q=violate+if+there+are+any+parametrized+constructors&oq=violate+if+there+are+any+parametrized+constructors&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIJCAEQIRgKGKABMgkIAhAhGAoYoAEyCQgDECEYChigATIHCAQQIRifBdIBCDExMjlqMGo3qAIUsAIB&client=ms-android-google&sourceid=chrome-mobile&ie=UTF-8

For https://checkstyle.org/checks/coding/matchxpath.html#Example2-config

And nothing is found :).
Sad, but still think this page is best location for such examples with low efforts from our side.