Fix/open second viewer on the given port #940

Job	Run time
🔍 Check if pull request	4s
⬢ Prepare Node.js	36s
🐍 Prepare Python	37s
🧱 Build test matrix	7s
📝 Build API docs	37s
🗃 Build datasets	2m 24s
🧱 Build Spotlight	4m 40s
🔍 Check	2m 24s
🧪 Doc Test	1m 17s
🧪 Unit Test	1m 21s
🧪 Integration Test (ubuntu-latest, 3.8)	11m 2s
🔍 Check wheel contents	43s
🧪 UI Test (chrome)	3m 50s
🧪 UI Test (firefox)	4m 50s
🚀 Release Spotlight	0s
	34m 32s

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