apt: Fix update command

apt: Fix update command

Use v1.10.0 everywhere

apt: Update package cache prior to installation

Makefile: Remove registry auth as public access is now allowed

README.md: Add sections for requirements and examples

pipeline: Use v1.8.0 masse gateway and schema

schema: Support expansion of existing environment variables

Support a `state.#Env.expandVariables` option that tells the compiler to
expand existing variables within other environment variable values.

This is essential for supporting use cases where an existing environment
variable needs to be appended, such as `{ PATH: "$PATH:/other/bin" }`.

pipeline: Use v1.7.0 masse gateway and schema

pipeline: Define `publish-schema` Makefile target