Template:Categories by decade

Categories by decade: A navigation box for the various master categories by decade, since there isn't a consistent naming convention for the categories. Created as a template so that it only needs to be updated once in 2020 instead of ten times.
 * The 1900s
 * The 1910s
 * The 1920s
 * The 1930s
 * The 1940s
 * The 1950s
 * The 1960s
 * The 1970s
 * The 1980s
 * The 1990s
 * The 2000s
 * The 2010s