Add "Manifesto Relevancy" column to learning content tables #18

Make it easy for readers to see how each Learning Hub item directly relates to which parts of the GRC Engineering Manifesto (in terms of Values and Principles). This also will act as a forcing function for maintainers of the Learning Hub to ensure that new additions to it align directly with the Manifesto - anything that doesn't align either shouldn't be included or should prompt a Discussion about updating the Manifesto.