Release v5.3.0

[github-actions]

Plain text now sits on the position it was given. It used to be drawn eight
pixels down and to the right of it - the padding a framed style needs between
its border and its words, which plain words have no use for - so a centred label
never landed on the thing it labelled: a number put at the middle of a line came
out beside it. The words are now centred on their position, the way a sprite put
there is.

A width too narrow to hold a single letter no longer wraps the words at all. It
used to turn them into a column of one letter per line: new Text("42", x, y, 1)
drew a 4 above a 2. Line breaks written into the text are still kept.

Text can also be layered like a sprite: goToFrontLayer(), goToBackLayer(),
goLayersForwards(int) and goLayersBackwards(int) decide which of several
overlapping texts is on top. Texts are drawn above the sprites, so this orders a
text against the other texts.

A class that extends Window and has a main method which is not static no
longer fails with "Cannot create multiple Windows!". Since Java 21 the JVM
builds an instance of such a class before it calls main, so the
new MyWindow() inside main was the second window and the project stopped
before it started. That window is now reused, and a note explains how to be rid
of the extra one by making main static. Two windows asked for by the project
itself are still an error.