Implement XSS prevention measures

[stypr]

Please consider adding XSS countermeasures for this product. It's possible to run an arbitrary JavaScript code.

To reproduce

1. go to https://letsmarkdown.com/
2. Get the generated URL ( https://letsmarkdown.com/pink-things-6832 )
3. Add the following details

<img src=1 onerror="console.log(top.document.body.innerHTML='Unexpected_Page')">

4. Ask people to access https://letsmarkdown.com/pink-things-6832

Suggested Fix

Consider disabling HTML feature on src/components/Score.tsx, or use the sanitizer package while HTML is turned on.

LetsMarkdown.com/src/components/Score.tsx

Line 30 in d88c75b

html: true,

I assume HTML tags are not required for the most of the time.

Reference: https://github.com/markdown-it/markdown-it/blob/master/docs/security.md

[Cveinnt]

Hi @stypr , thanks for pointing this out - really appreciate the effort!
I just pushed an update that fixes this with markdown-it-sanitizer. Let me know if you have any other suggestions security-wise!