Use externalInfoUrl for custom rules

[nicolas1bruno]

Is your feature request related to a problem? Please describe. When running Apex PMD with a custom ruleset, with custom rules in it, the url provided in the problems tab is invalid

Describe the solution you'd like The Apex PMD extension should prioritize the URL provided in the externalInfoUrl, available on the ruleset schema

Additional context In the current version the url is fixed, see ApexPmd.ts#L241

https://github.com/ChuckJonas/vscode-apex-pmd/blob/74ec3e52111151b5ee6e41afe2942689a230541e/src/lib/apexPmd.ts#L241-L244