build: make Dockerfile compatible with podman and other fixes

[joanise]

PR Goal?

make our Dockerfile compatible with podman for the orange DAC

Fixes?

• update .dockerignore to include all venv
• remove SHELL=, not supported by podman, not needed anyway since it just redeclared the default
• (slightly) better documentation
• remove py3-numpy apk package since pip then just reinstalls a different version
• remove cloning g2p since requirements.txt already get g2p@main from github

Feedback sought?

rubber stamping

Priority?

low

Tests added?

no

How to test?

podman build --tag ras .
podman run --rm ras

Confidence?

high

Version change?

no

[semanticdiff-com]

Review changes with  

[github-actions]

CLI load time: 0:00.04
Pull Request HEAD: 3890bb452e6de5e2a8862b785c5336e7d5bb7f89
No imports take more than 0.1 s.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.59%. Comparing base (c97f5f2) to head (3890bb4).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #291   +/-   ##
=======================================
  Coverage   88.59%   88.59%           
=======================================
  Files          22       22           
  Lines        1885     1885           
  Branches      309      309           
=======================================
  Hits         1670     1670           
  Misses        178      178           
  Partials       37       37           

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