[ADD] web_editor_class_selector: new module to add custom CSS in HTML editor.

This module allows users to create custom CSS classes, which can then be selected and applied directly in the HTML editor.

web_editor_class_selector/models/__init__.py

@@ -0,0 +1 @@
+from . import web_editor_class

web_editor_class_selector/models/web_editor_class.py

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+from odoo import fields, models
+
+
+class WebEditorClass(models.Model):
+    _name = "web.editor.class"
+    _description = "Web editor class selector"
+
+    name = fields.Char(required=True)
+    class_name = fields.Char(
+        required=True,
+        help="The class name to be added to the tag. It must be created in the CSS file.",
+    )
+    active = fields.Boolean(default=True)
+
+    _sql_constraints = [
+        ("class_name_uniq", "unique(class_name)", "Class name must be unique")
+    ]