Source code: https://github.com/olekstomek/automatic-period-after-double-space-web-browser-extension

This extension will slow you down on not using the period. All you have to do is use a space twice at the end of the sentence. This way you get a period at the end of the sentence and a space. You can keep writing your text. Example: This is the first sentence[space][space] This is the second sentence[space][space] You will receive as a result: This is the first sentence. This is the second sentence.

To avoid problems, the script does not work in password fields.