feat: add type-safety to github expressions

[tusharmath]

To make Github Expressions type-safe we have started work in https://github.com/tailcallhq/gh-workflow/blob/main/src/expr.rs

However, it still needs to support the following APIs:

• github
• env
• vars
• job
• jobs
• steps
• runner
• secrets
• strategy
• matrix
• needs
• inputs

Refer to the documentation for workflows over here - https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/accessing-contextual-information-about-workflow-runs#inputs-context