Check out carbone.io
It’s not super powerful but does the trick for basic stuff. They have both self hosted and a cloud/paid version.
pspdfkit.com might also have something for rendering PDFs as a service.
If you are looking for a quick way to get up to speed with flexbox or css-grid you should check out
https://flexboxfroggy.com/
and
https://cssgridgarden.com/
They are fun little tutorial games that introduce the basics
A heat-map of sorts for a codebase showing the files that have the most-frequent/most-recent edits as hottest. Purpose being to help acclimate new developers to a project by easily seeing which parts of the codebase are most actively worked on.
Gitlab is using Monaco for this. An open sourced online editor brought to you by none other than Microsoft. (https://github.com/Microsoft/monaco-editor)
I couldn't dig it up now but I recall seeing that Microsoft started this project as an online code editor for Azure, later using it in VSCode. So it would not be surprising if they bring this to github some time in the future.
It still is "alive" somewhere in Azure but MS scrapped it really and focused making the best possible Desktop Editor. You wont see a web editor form them soon.