datagrid-full.js initializes TomSelect without clear_button plugin

[foxycode]

This means there is no way to clear a selected filter value. Once a user selects a filter value, there is no UI affordance to clear it back to the empty/unfiltered state - other than using the "Reset filter" button which clears all filters at once.

The issue is easy to reproduce at https://examples.contributte.org/datagrid-skeleton/outer-filters/

Suggested fix:

1. In datagrid-full.ts (line 48):

// Before:
new SelectpickerPlugin(new TomSelect(Select)),

// After:                               
new SelectpickerPlugin(new TomSelect(Select, {
    plugins: ['clear_button'],
})),

2. Would be also nice to add CSS to hide the clear button when no value is selected (placeholder state):

.ts-wrapper.single:not(.has-items) .ts-control .clear-button {
    display: none;
}

Maybe related to #671

[radimvaculik]

Fixed in #1280.

TomSelect is now initialized with clear_button and dropdown_input plugins, plus maxOptions: null to remove the default limit on visible options.

The suggested CSS for hiding the clear button when no value is selected is not needed — the clear_button plugin's own SCSS already handles this via opacity transitions tied to the .has-items class.

[foxycode]

@radimvaculik Looks ok, works without custom CSS for me.

Probably not deployed to https://examples.contributte.org/datagrid-skeleton/outer-filters/