feat(builder): Introduce templating for prereq commands

[javorszky]

Closes #123

Adds templating to prerequisite commands

• moves the logic to do that onto the Prereq struct and out of the builder
• adds tests
• adds make target for easier local vendoring (not related to functionality)
• reorders imports

[javorszky]

Hm, interesting that a new commit does not dismiss the approval. 🤔