[opentelemetry-php-contrib] Add support for Joomla

[cbos]

At this moment there is no auto instrumentation support for Joomla.

Based on the available other auto instrumentation implementation I gave it a try and implemented it in this repo:
https://github.com/cbos/opentelemetry-auto-joomla

I am fine to make this part of opentelelemetry-php-contrib as well.
What would be right steps to do that?

[ChrisLightfootWild]

Hey @cbos 👋 that's great, thanks for offering your support!

Typically, just fork the https://github.com/open-telemetry/opentelemetry-php-contrib repo and copy some existing instrumentation across into src/Instrumentation. Given you had used the Wordpress instrumentation as a reference point, it is probably a good to copy the layout of that.

Once you open a PR, there is the EasyCLA to sign to allow the contribution to be accepted. This would be automatically linked on the PR but is worth being aware of.