Add a roadmap_to_1.0 document to developer_resources/

These questions come up for every new plugin:

- How can I tell if a django-simple-deploy plugin can support a particular platform/ workflow?
- How do I get started implementing a plugin for a particular platform?
- How do I know when it's ready for a 1.0 release?

Tasks
---

- [ ] Generate a doc in developer_resources/ that writes a customized *Roadmap to 1.0* doc that can be used to guide development, and as a broad first issue.
- [ ] Merge
- [ ] Share with existing plugin maintainers who might find value in this.

Start by reviewing the plugin-development questions listed in the issue and the repository's plugin-template context. Create a customized Roadmap to 1.0 document under developer_resources/ that addresses platform support, implementation steps, and release readiness. Done means the document is generated, merged, and shared with relevant plugin maintainers.

Written by the indexing model from the issue text.