[FEATURE] Automatic Dependency Updates

[pfuhrmann]

Is your feature request related to a problem? Please describe.
There are some CVEs always appearing in any image. It's important to keep the images up to date. This is somehow related to #108.

Describe the solution you'd like

• Integrate Mend Renovate updates including auto-merge GitHub actions functionality to keep the image up to date.
• Change Dockerfile base version to something more concrete to keep getting a fresh image every time patches are released. e.g. node:20.6.1-alpine3.18.
• Release the new image version on every PR merge automatically.

Describe alternatives you've considered
The alternative is to keep the echo-server updated by hand. It's time-consuming for the authors. Another alternative is GitHub Dependabot, however, it does not come with the same "bells and whistles" as Renovate.

Additional context
The current CVE in ealen/echo-server:0.7.1: https://nvd.nist.gov/vuln/detail/CVE-2022-48174.

Base Score: 9.8 CRITICAL

[Ealenn]

Hello ! Thanks for this tools 🙏 I see some issues about security risk, for information I created this project mainly to test/simulate gateway on local or dev environments, so I'm not really worried about security. But isn't the case for all users (see #108) I will push another MR soon to rearrange this project accordingly to the different reports.

[pfuhrmann]

Updates seems to be working nicely. Thank you for your hard work, this image is great!