Add to styleguide, how to mark-up property values

[kd-ods]

Broadly, in the docs we mark up a non-object value of a property using single quotes, eg:

the interests which make the person meet the criteria for being declared a beneficial owner MUST be included if known. They MUST have beneficialOwnershipOrControl set to ‘true’. If an interest is known to be exercised indirectly, via intermediary entities then directOrIndirect MUST be ‘indirect’. If it is known to be exercised directly then directOrIndirect MUST be ‘direct’. Otherwise directOrIndirect MUST be ‘unknown’.

But this isn't noted in the style guide and there are instances in the docs where property values are marked up by property names:

[...] represented using only these interest.type codes:

• nominator
• nominee