add theme to RTD #1019

Job	Run time
Run_Installer (ubuntu-latest)	51s
Run_Installer (macos-14)	1m 7s
Download_Data	10s
Unit_Tests (ubuntu-latest)	1m 3s
Pipelines (ubuntu-latest, metadetect)	18m 47s
Unit_Tests (macos-14)	1m 27s
Pipelines (ubuntu-latest, metacal)	4m 43s
Pipelines (ubuntu-latest, redmagic)	3m 27s
Pipelines (ubuntu-latest, lensfit)	5m 47s
Pipelines (ubuntu-latest, metadetect_source_only)	4m 8s
Pipelines (macos-14, metadetect)	23m 51s
Pipelines (macos-14, metacal)	14m 56s
Pipelines (macos-14, redmagic)	13m 23s
Pipelines (macos-14, lensfit)	14m 19s
Pipelines (macos-14, metadetect_source_only)	9m 11s
	1h 57m 10s

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