With https://whereby.com/ you can provide video meetings in the browser. Your attendees just need to visit your custom link to whereby.
You can also share your screen and for small teams (up to 4 attendees) it is gratis.
This is not a code library but a software recommendation. Anyway, i hope this helps.
If you are looking for software (self-hosted):
You should provide more information about the platform you're using. There are lots of solutions that exist for this. Here is one for WordPress. There are more for Django, Ruby on Rails, JavaEE, etc.
Your platform is important because, unless you want to use some innovative blockchain like Bitmessage (in which ...