Content editable remove unnecessary tags with content and all html tags on paste

Good snippet to control what formatting is retained in a rich text editor on pasting data.

We have been wanting to create a rich-text editor where we can control the tags and attributes that are permitted.

Tags added in a rich text editor (through contenteditable) in multiple ways:
- On pasting some rich text
- Keyboard shortcuts such as ctrl b, ctrl i
- Our own commands executed through document.execCommand

We can use a similar technique of tag replacement by tying the clean-up to oninput event.