Without getting into the "two spaces" = "old, typewriter days, should not do"
conversation.
Under Tools, Options, Spelling & Grammar, Settings button, you can select
who many spaces you want between sentences. This will not "automatically"
create the spacing but it will highlight (with green squiggle) any sentence
gaps that are not what you set this number as, and it will give the
right-click option to change to you requirements.
Needless-to-say- I have this number set to 1 in my seetings.
Hope this helps
DeanH