NEWS and CONTRIBUTORS for Isabelle2025

[Makarius]

Dear Isabelle contributors,

now is a good time to check that NEWS is complete for the forthcoming 
Isabelle2025 release --- concerning "user-relevant changes", i.e. everything 
that improves (or affects) regular use of Isabelle. That is non-optional.

In addition, a brief summary with time (range), name(s), optional affiliation 
may be added to CONTRIBUTORS. That is optional: Sometimes there are reasons to 
emphasize contributions, and sometimes there are reasons not to.


As usual, I will be busy in the coming weeks to sort out pending discussions 
that are relevant to the release.


	Makarius