All from Material Design Icons.

Glyphs in the Private Use Area at uE000 will no longer conflict with
fallback fonts in the "extra keys" option.

The new key switches to any installed "voice" input method.
If several input methods matches, no effort is made to choose.
Might misbehave with some input methods other than Google's on API < 28.

It is placed on the middle of the arrows on the bottom bar. It is
enabled by default and can be removed in the "Extra keys" option.

The key is not removed from the keyboard if no voice input method
exists.

Added missing accent (horn, hook, dot below)
Added layout
Added accent font svg (by modified existing accent)

The small bar on the middle of the dotted circle looked like a small
arrow. Make the bar span the whole circle, not on the middle.

A new option allow to choose a secondary layout, the switching key is
placed on the top edge of the space bar.

The "Programming layout" option was basically doing that but it was
possible to choose from a few layouts only. It is improved and renamed.

The 'LayoutListPreference' allows setting the string for the first entry
but otherwise share the rest of the array.

Add nice icons from materialdesignicons.

Allows to type many of the "with stroke" or "with bar" latin letters.

The key enable caps lock immediately. It does nothing if caps lock is
already enabled.

It is not present on the keyboard by default but a place is defined on
every layout, top-right of the shift key. It can be enabled in the
settings.

The icon is from materialdesignicons.com.