Add history entry for paraemter order change.

[TorkelE]

Now the history file starts like this:

Breaking updates and feature summaries across releases

Catalyst unreleased (master branch)

• BREAKING: The order of the parameters in the ReactionSystem's .ps field has been changed (only when created through the @reaction_network macro). Previously they were ordered acording to the order with which they appeared in the macro. Now they are ordered acoridng the to order with which the appeard after the end part. E.g. in

  rn = @reaction_network begin
    (p,d), 0 <--> X
  end d p

  previousl the order was [p,d], which now it is [d, p].

Catalyst 10.1

• Added support for @unpack observable_variable = rn and
  rn.observable_variable. This requires a new inner constructor definition for
  ReactionSystems, but is not considered breaking as the inner constructor is
  considered private.
• Support added for ModelingToolkit 7 and Symbolics 4.