Not so long ago, I wrote about a handy Add-On for Google Drive called Speech Recognition, here. It allows the user to talk into the microphone and have their words transcribed. Google has now incorporated Voice Typing in their Tools Menu, which does the same thing!
A microphone icon will appear on the side of the document. Click it. The first time you use this feature, you will be prompted to allow Google Docs to use your microphone. Choose allow and start talking.