client spec

[justinmk]

Followup to #41 which specifies the "package spec" (dependencies format).

Separate from the "dependencies format", next thing to define would be client behavior. E.g.:

Defined client behavior

• download all dependencies
• download order is undefined?
• save them to a standard location? or is this undefined?
• show an error if transitive dependencies have conflicting versions?
• scripts lifecycle: client finds scripts in directory specified by "scripts"
  • or undefined / client-defined?
    • Nvim plugin convention: lua/pkg/build.lua