docs: Better explain how to use the components #2903

Job	Run time
Static analysis	1m 35s
Dependencies, Unit tests (18)	1m 45s
Dependencies, Unit tests (20)	1m 48s
Dependencies, Unit tests (22)	1m 33s
Build application (govuk-docs)	2m 9s
Build libraries	2m 10s
Build application (govuk-template)	1m 37s
Build application (next-example)	1m 33s
Test application (govuk-docs, chromium)	1m 32s
Test application (govuk-docs, firefox)	1m 44s
Test application (govuk-docs, electron)	1m 10s
Test application (govuk-template, chromium)	1m 54s
Test application (govuk-template, firefox)	1m 45s
Test application (govuk-template, electron)	1m 41s
Test application (next-example, chromium)	1m 39s
Test application (next-example, firefox)	1m 22s
Test application (next-example, electron)	1m 8s
	28m 5s

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