Add `--help-json` flag for machine-readable CLI help #6867

Job	Run time
Retrieve all template features	6s
RunTestWorkflow (multiqc)	1m 46s
RunTestWorkflow (modules)	1m 1s
RunTestWorkflow (changelog)	2m 19s
RunTestWorkflow (github_badges)	2m 5s
RunTestWorkflow (nf-test)	2m 13s
RunTestWorkflow (license)	2m 23s
RunTestWorkflow (igenomes)	2m 8s
RunTestWorkflow (rocrate)	2m 6s
RunTestWorkflow (seqera_platform)	2m 4s
RunTestWorkflow (gpu)	2m 7s
RunTestWorkflow (documentation)	2m 5s
RunTestWorkflow (fastqc)	1m 48s
RunTestWorkflow (code_linters)	2m 2s
RunTestWorkflow (nf_schema)	2m 21s
RunTestWorkflow (nf_core_configs)	2m 3s
RunTestWorkflow (email)	2m 26s
RunTestWorkflow (all)	49s
RunTestWorkflow (codespaces)	2m 7s
RunTestWorkflow (citations)	2m 15s
RunTestWorkflow (vscode)	2m 32s
RunTestWorkflow (ci)	2m 13s
	42m 59s

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