Use Chrome Dev Tools
If you want to use chrome, but not a chrome extension, you want to use the console in the Chrome Dev Tools. Running a script for a website on the Chrome Console is a solution to your question, and is shown below, but it will disappear when you refresh the page.
Replacing String Literals in the Body
To replace all instances of dogs
with doggos
in the HTML body, you would walk the document tree as documented by this SO question.
Applied to your question, the result is below:

Further Reading
You may also want to check out javascript with Regular Expressions, which are more powerful than a simple string replace. If you want this running in the background, you should look at Mutation Observers to check whether the DOM has changed.