Summary of important user-visible changes for datatypes 1.2.7:
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 ** The `datetime` class gains a large set of operations, as its
    implementation continues incrementally.  Newly available: arithmetic
    `plus`/`minus` and the `:` range operator; the relational operators
    `lt`/`le`/`gt`/`ge`/`eq`/`ne` together with `isequal`/`isequaln`;
    ordering with `sort`/`issorted`, `sortrows`/`issortedrows`, `min`/`max`,
    and `unique`; the set operations `intersect`/`union`/`setdiff`/`setxor`/
    `ismember`; `diff` (returning a `duration`) and `caldiff`/`between`
    (returning a `calendarDuration`); the interval test `isbetween`; the
    reductions `mean`/`median`/`mode` (returning `datetime`) and `std`
    (returning a `duration`); and `dateshift`.  All are timezone- and
    DST-aware.

 ** Updated the bundled IANA timezone database to version 2026c (issue #36).

 ** Added `%!demo` example blocks for the `table`, `categorical`,
    `duration`, `calendarDuration`, and `string` classes, and for the
    `table` file-I/O helper functions.  Table demos now also show the input
    table, not just the result.

 ** Modernized docstrings across the package: removed empty `@multitable`
    spacer columns, added missing Name/Value headers, and use `*` for
    multiplication inside `@math` expressions.
