Copy as plain text is a simple single-purpose extension.
Its name pretty much says it all:
- Highlight text in Chrome
- Right click the mouse and select the Copy as plain text option
- Paste the now unformatted text into wherever you need it
You could achieve the same effect by using the shortcut Ctrl Shift V to paste copied content as unformatted text. Using the extension takes away the need to remember another shortcut however.