bug#52173: `ś' character not available using `C-x 8'

[Juri Linkov]

> `ś' is a character used in /e.g./ Polish.  Currently `C-x 8 ' s' is not
> bound.  Could this be added (along with the capitalized variant)?

Whereas adding this to `C-x 8 ' s' would be fine, an existing
alternative is to type `C-x \ ' s' after selecting the
input method `compose'.

Also cycling input methods proposed by Robert would be nice -
desktop/window managers support cycling by typing
the keyboard-layout switching key several times
when 3 or more layouts are selected.