That function exist by default in all major browser. In firefox it's called "reader view".
In chrome you have to
visit chrome://flags/#enable-reader-mode
then
Enable the option “Enable Reader Mode.”
Click the “Relaunch” button that appears at the bottom to relaunch Google Chrome.
Now you can visit any website or webpage with long readable text.
Click on the book icon on the right of the address bar to enable reader mode.
