Allow customize all symbols input

[kanru]

Is your feature request related to a problem? Please describe.

Currently we have 3 different symbols input methods

1. Symbols menu triggered by the ` key. This can be customized by editing the symbols.dat file.
2. Easy symbol input triggered by Shift + key. This can be customized by editing the swkb.dat file, and the mapping is not limited to symbols.
3. Various symbol input triggered by Shift key, for example all punctuation marks like ， and 「」. Usually there is secondary symbols menu available. This is currently static data in code.

Describe the solution you'd like

Simplify case 2 and 3 by recording all Shift triggered symbols input in swkb.dat.
Simplify case 1 and 3 by recording all alternative symbols in the symbols.dat file.

Describe alternatives you've considered

Extract the static data used by case 3 to another config file.

Additional context
Add any other context or screenshots about the feature request here.