add example record with external provenance link

[tomkralidis]

An example of provenance metadata can be found in the WMO Climate Data Catalogue Key Climate Indicators.

[tomkralidis]

We could express provenance in WIS2 metadata as follows:

{
    "type": "text/html",
    "rel": "describedBy",
    "title": "Provenance information for this dataset",
    "href": "https://jjk-code-otter.github.io/demo-dash/Dashboard/dashboard.html"
}

Now, to make the link more succinct, I would suggest the webpage at https://jjk-code-otter.github.io/demo-dash/Dashboard/dashboard.html includes "anchors" such that one can then like as follows:

{
    "type": "text/html",
    "rel": "describedBy",
    "title": "Provenance information for this dataset",
    "href": "https://jjk-code-otter.github.io/demo-dash/Dashboard/dashboard.html#HadCRUT5"
}

(notice the #HadCRUT5 addition to the href above, which would, when a user clicks, take the user directly to that dataset’s provenance information (vs. having to scroll through).