Add `--help-json` flag for machine-readable CLI help #6859

Job	Run time
Retrieve all template features	6s
RunTestWorkflow (igenomes)	13s
RunTestWorkflow (ci)	13s
RunTestWorkflow (fastqc)	13s
RunTestWorkflow (seqera_platform)	13s
RunTestWorkflow (multiqc)	13s
RunTestWorkflow (modules)	13s
RunTestWorkflow (changelog)	13s
RunTestWorkflow (license)	13s
RunTestWorkflow (nf-test)	13s
RunTestWorkflow (nf_core_configs)	13s
RunTestWorkflow (documentation)	13s
RunTestWorkflow (nf_schema)	13s
RunTestWorkflow (all)	13s
RunTestWorkflow (code_linters)	13s
RunTestWorkflow (vscode)	13s
RunTestWorkflow (rocrate)	13s
RunTestWorkflow (citations)	13s
RunTestWorkflow (codespaces)	13s
RunTestWorkflow (github_badges)	13s
RunTestWorkflow (gpu)	13s
RunTestWorkflow (email)	13s
	4m 39s

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