Clarify full text search is limited to support site content

[loricooperhdf]

From Elena's suggestions:

The full-text search is a great feature for searching within HDF5 documentation. Could you consider either expanding its scope to include wider web results or clearly indicating that the search is limited to the support portal?

[loricooperhdf]

https://support.hdfgroup.org/documentation/hdf5/latest/_f_t_s.html

Perhaps add
This search pulls from all content hosted on the support.hdfgroup.org URL and covers the entirety of HDF5 documentation produced by The HDF Group.

I looked at the code to see if I could figure out why the input box was so small, but instead noticed that with a more narrow browser window, the search input box became wider. This happened in Chrome and Safari. Can we briefly look into this and see if we can have a wider search input box consistently.