fix: delimiter dropdown

[Plekest]

Fix dropdown delimiter option for multiple selection

The delimiter column option was not being respected when using type: 'dropdown' with multiple: true. Selected values were always
joined using the hardcoded jSuites internal separator (;) instead of the configured delimiter.

Root cause: Three places in the code had hardcoded ';' instead of reading column.delimiter:

• editor.js — splitting the stored value when opening the editor
• editor.js — joining selected values when saving on close
• internal.js — splitting the stored value when rendering the cell label, and joining for display

Changes:

• When opening the editor, split the current value using the configured delimiter
• When closing the editor, retrieve values as array from jSuites and join with the configured delimiter
• When rendering the cell, split and display using the configured delimiter