Add helpful PyQt env vars

[jacob-curley-fnal]

Added some environment variables to the devcontainer.json that help with displaying PyQt apps correctly in the container's "desktop". Without these, the top of the app (including its menu and window buttons) won't display.

[github-actions]

Code Coverage Report - 46 of 117 lines covered ( ⛔ 39.32%)

src - 46 of 117 lines covered ( ⛔ 39.32%)

src/ap_python_starter_kit - 46 of 117 lines covered ( ⛔ 39.32%)

src/ap_python_starter_kit/init.py - 0 of 2 lines covered ( ⛔ 0.00%)

⛔ This file is missing coverage.

src/ap_python_starter_kit/acsys_client.py - 9 of 28 lines covered ( ⛔ 32.14%)

Uncovered lines: ⚠️ 18-19, 21-24, 26-28, 30, 34, 36-38, 40-41, 45-46, 48

src/ap_python_starter_kit/gui.py - 16 of 65 lines covered ( ⛔ 24.62%)

Uncovered lines: ⚠️ 12-13, 20-23, 25-26, 28-31, 33-34, 36, 39, 42, 45, 51, 58-59, 61-65, 67-68, 70-73, 75, 77-82, 84-85, 87-88, 90-91, 95-98

src/ap_python_starter_kit/main.py - 21 of 22 lines covered ( ✅ 95.45%)

Uncovered lines: ⚠️ 47