Go to Stackoverflow, find a code snippet. A 'COPY' button will be added at the top-right corner. If you don't know what Stackoverflow is, you probably don't need this.
Example: https://stackoverflow.com/a/47403292/529187
Checkout my another Chrome extension - https://chrome.google.com/webstore/detail/web-sequence/kcpganeflmhffnlofpdmcjklmdpbbmef
谷歌浏览器、其他Chromium内核的浏览器