Update "Create a plugin docs" to be a how to create a plugin end to end

### Is your feature request related to a problem? Please describe

https://github.com/asdf-vm/asdf/blob/master/docs/plugins/create.md has decent documentation, but I think it would be superior if it was written from the perspective of taking one of the most popular asdf plugins and creating it from scratch talking about things like:

- adding env specific vars for runtimes such as go's GOPATH
- how to support multiple architectures e.g. linux,windows,arm,etc.
- how to compile from source (if needed) or if that is not a goal of asdf, outline it in the docs.

if the docs were written in this way, I'd be more than happy to contribute, but I'm just not familiar enough with the goals of asdf or bash for that matter.

it would also help people build plugins consistently since there is possibility to have such a wide variety, I think documentation from this perspective would be incredibly useful for the community and the overall growth of asdf.

A good example of documentation written this way is: https://storybook.js.org/docs/react/writing-stories/introduction

they show code, and explain it fairly well, which to me is a much more approachable way to learn.

### Describe the proposed solution

outlined above.

### Describe similar `asdf` features and why they are not sufficient

outlined above.

### Describe other workarounds you've considered

outlined above.

Start with docs/plugins/create.md and review its current plugin-creation guidance, then compare the requested end-to-end perspective with the linked Storybook example. Define the documentation scope for environment-specific variables, multiple architectures, and compiling from source, and consider the project’s plugin goals before updating the guide.

Written by the indexing model from the issue text.