There is an integrated settings/extensions sync feature (not yet available on the main release, probably next month). [1]

Or there is a popular extension that does exactly the same thing. [2]

Or you can also do it manually, import/export your settings in JSON and generate a list of `code --install-extension x` that you run on your other machines. [3]

[1] https://code.visualstudio.com/docs/editor/settings-sync

[2] https://marketplace.visualstudio.com/items?itemName=Shan.cod...

[3] https://stackoverflow.com/a/49398449/652669