Update text to synchronise with Committee site

[ronaldtse]

The committee site description of the resource sites:
https://committee.iso.org/sites/tc211/home/re.html

Had a discussion with Agneta and @MatsAhlin today and that the resource sites landing page should be synchronised with the committee site description.

As a way moving forward, @MatsAhlin may directly edit the content of this page to synchronise with the committee page.

In the short term, I will update the text.

[ronaldtse]

I've done my part.