This is a software problem. Programs that display proportional text should recognize one or more spaces after a period as a sentence break and should render appropriately.
. . . unless it's not a sentence break, as in the case of "Mrs. Rigsby" or "etc. etc. etc.", or any of dozens of other options.
On the other hand, software configured to recognize two spaces after a period is far more likely to work properly for identifying sentence endings, as long as you type two spaces between sentences.
On the other hand, software configured to recognize two spaces after a period is far more likely to work properly for identifying sentence endings, as long as you type two spaces between sentences.