Make frontend docker config more configurable

[JonasGilg]

Description

This PR makes the docker setup for the frontend configurable.

Design Decisions

This PR adds two new configuration variables for the frontend:

• ESID_PORTS: Defines the ports under which ESID is published.
• ESID_BRANCH: Gives a distinct name to the created image.

This allows multiple images with multiple ports to be deployed on the same server.

Checklist

I, the author of this PR checked the following requirements for good software quality:

• The code is properly formatted (I ran the formatter)
• The code is written with our software quality standards (I ran the linter)
• The code is written using our code style
• Extensive in source documentation has been added
• Unit and/or integration tests have been added
• All texts have been internationalized with at least the following languages:
  • English
  • German
• I tried addressing all new accessibility problems displayed in the console and documented if they can't be fixed
• I attached performance measurements to prevent performance degradation
• I added the changes to the next release section of the changelog

I, the reviewer checked the following things:

• I ran the software once and tried all new and related functionality to this PR
• I looked at all new and changed lines of code and commented on possible problems
• I read the added documentation and checked if it is understandable and clear
• I checked the added tests for completeness
• I checked the internationalized strings for spelling errors
• I checked the performance metrics for problems or unexplained degradation
• I checked that the changes are noted in the changelog

[github-actions]

Unit Test Results

  1 files  ±0  14 suites  ±0   24s ⏱️ -10s
32 tests ±0  32 ✔️ ±0  0 💤 ±0  0 ❌ ±0 
33 runs  ±0  33 ✔️ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit d69b811. ± Comparison against base commit 0c3edc9.

♻️ This comment has been updated with latest results.