Be able to configure meta-data with rules (and pass them to reports)

[nikku]

Proposed Changes

As described in #18, this allows rule authors to configure meta in a rule. The meta-data will be passed along with reports so downstream integrators, can, i.e. ship custom documentation URLs with their rules (camunda/camunda-modeler#4491).

Example rule (exposing a documentation URL)

module.exports = function(config) {
  return {
    meta: {
      documentation: {
        url: 'https://github.com/bpmn-io/bpmnlint'
      }
    },
    check: (node, reporter) => {
      ...
    }
  };
};

Example accessing the documentation URL from a report

const url = report.meta?.documentation?.url;

What's inside this PR

This PR is comprised in two parts:

• 038a2cb adds meta support
• 95be026 adds a transform hook that allows integrators to attach and/or modify existing rules (whereas the purpose is on modifying meta-data, i.e. overriding documentation URLs, or attaching them)

Checklist

To ensure you provided everything we need to look at your PR:

• Brief textual description of the changes present
• Visual demo attached
• Steps to try out present, i.e. using the @bpmn-io/sr tool
• Related issue linked via Closes {LINK_TO_ISSUE} or Related to {LINK_TO_ISSUE}

---

Closes #18

Depends on #163

[barmac]

Looks good