docs: clarify Sourcegraph endpoint/token are required, recommend env … #25

Job	Run time
Resolve release tag	4s
Build wheel	19s
Validate / Detect changed paths	3s
Validate / Lint Markdown	17s
Validate / Lint GitHub Actions	5s
Validate / Validate Python	17s
Validate / Build and smoke-test package	0s
Validate / Validate package	4s
Publish GitHub release assets	6s
Publish PyPI package	18s
	1m 33s

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