Allowing "tasks" instead of only allowing "pipeline" in turbo.json

[AlfreddGco]

Issue Description

Nixpacks does not support turbo versions >= 1.7. Specifically, turborepo.rs attempts to read turbo.json and looks for the "pipeline" key, but turbo versions 1.7 and above use the "tasks" key instead. This mismatch results in Nixpacks failing silently and throwing an error like "start command not found," without clearly indicating the underlying issue.

Additionally, the documentation does not explicitly state that only turbo versions < 1.7 are supported.

---

Possible Solutions

1. Downgrade turbo to v1.6: This is a temporary workaround, but it’s not ideal for users who rely on newer turbo features.
2. Add support for the "tasks" key in this repository: This would involve updating the code to handle turbo versions >= 1.7. However, it’s unclear whether this change only requires supporting the new JSON key or if additional implementation is needed to fully support newer turbo versions.

---

Proposed Fix

This PR implements Solution 2 by adding support for the "tasks" key in turborepo.rs. This ensures compatibility with turbo versions >= 1.7 while maintaining backward compatibility with older versions. The changes include:

• Updating the JSON parsing logic to check for both "pipeline" and "tasks" keys.
• Ensuring the build process correctly identifies and uses the appropriate commands from turbo.json.

[coffee-cup]

Great fix! Supporting both makes sense