Idea to auto-generate test builds

[dapplion]

Part of the DAppNode testing process includes generating a test version of the DNP_CORE package where part of its dependencies are IPFS hashes of not-yet-published versions.

Would be cool to have an automated process to generate this DNP_CORE version in the cloud and update it as the dependencies progress.

Idea / flow:

Have a template issue in DNP_CORE with specific text that would trigger a bot in a workflow

dnp-core-bot-trigger-issue

New packages : branches
- dappmanager:v0.2.38
- VPN:v0.2.15

When an issue with the tag dnp-core-bot-trigger-issue opens a workflow will build those branches and inject the resulting release hash in the DNP_CORE manifest, doing this script's job: https://github.com/dappnode/DAppNode/blob/master/scripts/dappnode-core-update.sh
And publish the resulting hash as an issue comment

Then, it could watch those repos for updates and rebuild

[pablomendezroyo]

Complementary of https://github.com/dappnode/DAppNodeSDK/pull/132/files