Update README.md

[kalmanh]

Add new tutorial resource - a video of filling out a medical claims form

What?

Adding new tutorial resource

Why?

I used pdf-lib to fill out a medical PDF form and created a video about how I overcame the particular challenges that I encountered

How?

N/A

Testing?

N/A

New Dependencies?

N/A

Screenshots

N/A

Suggested Reading?

N/A

Anything Else?

N/A

Checklist

• I read CONTRIBUTING.md.
• I read MAINTAINERSHIP.md#pull-requests.
• I added/updated unit tests for my changes.
• I added/updated integration tests for my changes.
• I ran the integration tests.
• I tested my changes in Node, Deno, and the browser.
• I viewed documents produced with my changes in Adobe Acrobat, Foxit Reader, Firefox, and Chrome.
• I added/updated doc comments for any new/modified public APIs.
• My changes work for both new and existing PDF files.
• I ran the linter on my changes.

[jonparker]

Thanks @kalmanh this video was really good. A great intro to filling pdfs with pdf-lib.