Download Agda binary if not exists in the path

[L-TChen]

Agda's CI/CD currently builds binaries for every commit on the master branch and produces the artefact https://github.com/agda/agda/blob/master/.github/workflows/deploy.yml

The extension can exploit the CI/CD to download artefact if agda is not found in the path.

[banacorn]

Where can I find binaries for official releases (non-nightly builds)?

[L-TChen]

We haven't released these binaries officially. Maybe the requested feature could be added as an "experiment feature". Then, once I sort out agda/agda#6384, we could make the feature official?

[banacorn]

Sounds good, we can start with the nightly binaries first!