Clarify that HTML is allowed in the field and will be rendered

Problem/Motivation

Great module, I love it!

I was hoping that I could build a link out of two separate "link text" and "link URL" fields with HTML, but assumed that HTML tags would be stripped.

But to my surprise, it worked, which is really nice.

Steps to reproduce

Proposed resolution

Document that HTML is accepted, and rendered, maybe by adding something like this on the project page, as well as in the README?

Supports HTML, for example:
<a href="[node:field_link_url]">[node:field_link_text]</a>

Remaining tasks

User interface changes

API changes

Data model changes