feat: add meeting link option

[bjohansebas]

To avoid repeating a template due to a link change, the option to add a link is included, reducing template duplication with a simple link

ref: expressjs/discussions#283

[bjohansebas]

I'll see if I can manage to pass the data option suggested in #206.

[jonchurch]

This is actually a lot simpler for now though and is worth considering

it's reasonable to think someone would provide meeting link as a baseline for a meeting action

[jonchurch]

Lets add it as a shorthand as well
https://github.com/pkgjs/meet#shorthand-in-your-custom-meeting-templates

Check the conversions.js file https://github.com/pkgjs/meet/blob/61042a30f295179c24673776877615fa12a6c0bc/lib/conversions.js#L13C1-L25C4

[jonchurch]

lets update the default meeting template to use meetingLink if it is available

The notes default doesn't have a meeting link section, so no need there

https://github.com/pkgjs/meet/blob/main/lib/default-template.js#L42

[jonchurch]

meant to request changes on the default template comment