Allow user to change font size on contentEditable

So I have created a website: Colors & Fonts Curated library of colors and fonts for digital designers and web developers.

( colorsandfonts.com )

the page in question is colorsandfonts.com/fonts.html

Now after working on the fonts and so on, I wonder how could I make the user know that the text is editable.

I am just a bit worried I get it too cluttered-...

thank you !