Add a running 'supported package managers' list

[OnyxAbove]

A list of all package managers supported by topgrade. Can be in Readme or elsewhere.

This is a more concise version of #960

[SteveLauC]

We should add this to https://topgrade-rs.github.io/

[OnyxAbove]

That is a good idea and definitely should be implemented as well as putting it in the README. I don't know about other people, but I check the main git repo before the website.

It is ultimately the decision of the current contributors where to put this list. I might work on this if nobody else has time, but as a student, I have little time aside from school.

Where might I be able to find the methods/functions for all of the package managers supported?

[SteveLauC]

Thanks for your interest in working on this!

Where might I be able to find the methods/functions for all of the package managers supported?

Type Step can be seen as a rough list of the supported tools, but, it has an issue of granularity, e.g., on-my-zsh and oh-my-bash, are not 2 Step variants, they both belong to Step::Shell. Step::Shell and Step::Vim are 2 known variants that suffer from this issue. Other variants may have this issue as well? But I haven't found them or received any complaints about them.

[OnyxAbove]

Ok, I will copy/paste into Readme tomorrow (probably) and add oh-my-zsh and oh-my-bash as well. Will submit a PR and make changes if needed.