build: add pipx to devcontainer #28

Job	Run time
Build Wasm	1m 48s
Build Web UI / Build Treemap WebUI	37s
Tests (ubuntu-latest, unit)	1m 16s
Tests (ubuntu-latest, integration-example)	2m 7s
Tests (ubuntu-latest, integration-real)	3m 23s
Tests (windows-latest, unit)	3m 4s
Tests (windows-latest, integration-example)	4m 19s
Tests (windows-latest, integration-real)	4m 42s
Tests (macos-13, unit)	1m 27s
Tests (macos-13, integration-example)	4m 18s
Tests (macos-13, integration-real)	5m 29s
Tests (macos-14, unit)	1m 9s
Tests (macos-14, integration-example)	2m 46s
Tests (macos-14, integration-real)	3m 43s
Tests on UI	44s
Build go-size-analyzer explorer	32s
Deploy explorer to GitHub Pages	8s
Merge Go test results (ubuntu-latest)	1m 32s
Merge Go test results (windows-latest)	1m 39s
Merge Go test results (macos-13)	1m 32s
Merge Go test results (macos-14)	1m 32s
	47m 47s

Provide feedback