Include link to upcoming changes for 4.0.2 on documentation page

We have had some issues with understanding and fixing an error on ODataOmitValues.Nulls (see https://github.com/microsoft/DataConnectors/issues/360#issuecomment-1015339087). It seems that this functionality will be part of 4.02.

Ultimately, Google was our friend to point towards https://issues.oasis-open.org/browse/ODATA-818 providing more background.

On the page https://www.odata.org/documentation/, I was unable to quickly find the content of 4.02 (or just too lazy to search more thoroughly, being part of the Do Not RTFM-generation).

The suggestion is to add a link to the tickets on issues.oasis-open.org from /documentation/ that define the cumulative planned contents of 4.02. In that way it becomes easier to find contents of upcoming 4.02.

Suggestion is to also add this link to the Getting Involved page on https://www.odata.org/contribution/.

Start with the source for the documentation page at odata.org/documentation/ and the Getting Involved page at odata.org/contribution/. Review the OASIS issue link referenced in the report and add links that expose the planned 4.0.2 contents from both pages. Done means visitors can find the upcoming-change information from each page.