add qt5 package (#55)

Qt 5.15.18-lts-lgpl (QtBase + QtCharts) built from source as shared
libraries. Provides headers, shared libs, and tools (moc, rcc, uic)
for building cabana in openpilot without system Qt5 packages.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pyproject.toml

@@ -13,6 +13,7 @@ members = [
   "libyuv",
   "nanosvg",
   "ncurses",
+  "qt5",
   "raylib",
   "zeromq",
   "zstd",