igr 0.2.0

• All functions now support tetrads (2 km squares, also known as "DINTY" system, e.g. "N85H") (#3).
• igr_to_ig() and st_igr_to_ig() can (optionally) return centroids of Irish grid references (#8).
• All functions have additional hardening against invalid parameters (#5).
• README & vignette refinements including compatibility with latest development version of tmap 4.0.0 (#4).

igr 0.1.1

• Description extended and vignette build technique adjusted for CRAN compatibility.