Support programmatic text in YAML metadata values

[Witiko]

Currently, we assume that all strings in YAML metadata are markdown text. Besides the jekyllDataString renderers, we should also produce e.g. jekyllDataProgrammaticString renderers, which would receive the raw text of the strings. Furthermore, we should also rename jekyllDataString renderers to e.g. jekyllDataTypographicString and deprecate the previous name.

Tasks

• Update unit tests.
• Declare jekyllDataProgrammaticString renderer and renderer prototype.
• Produce jekyllDataProgrammaticString renderer and renderer prototype.
• Rename jekyllDataString renderers and renderer prototypes to jekyllDataTypographicString.
• Deprecate jekyllDataString similarly to Rename renderers based on the semantics of elements #201.
• Add the changes from this ticket to CHANGES.md.
• Acknowledge ISTQB in CHANGES.md and README.md.