add integration with the Angel3 framework

[insinfo]

first i would like to thank you for your amazing work on this project, i've been working with dart for 7 years now developing fullstack applications in dart, using AngularDart and Angel Framework, and it's been a lot of pleasure using dart, before i used PHP/C# and javascript, although the dart has fewer tools and libraries with a small ecosystem because it is new, yet it has been very rewarding to work with dart because it is a much less verbose language than C# and PHP, I have contributed to several packages over the years based on what I'm going to need it, I read your article and was happy to see another developer using dart in the backend, dart has a lot of potential for the backend that is still untapped.

I still miss dart backend integration libraries with grafana/prometheus and seeing your work has left me with hope for an integration with Angel3

https://angel3-framework.web.app/#/about
https://github.com/dukefirehawk/angel
https://github.com/angulardart-community/angular

[Fox32]

I have no experience with the Angel3 framework, but I guess adding an integration should be similar to the shelf integration. There are some low level functions that you can use to create an endpoint that exposes metrics. Not sure if Angel3 supports something like middlewares, but if it does you could create a middleware that instruments all routes.