Proposing changes to documentation and JSON Schema

Added proposed documentation section explaining Numeric data object and also updated JSON schema to match changes.

I tested the numeric example with tap_action.data in the documented web editor. The current schema did not appear to reject the field,
likely because numeric tap_action does not currently forbid additional properties at that nested level. I still added data explicitly
to the numeric schema so it is documented, discoverable, and type-checked as an object.

config.schema.json

@@ -256,6 +256,11 @@
                 "action": {
                   "$ref": "#/$defs/action"
                 },
+                "data": {
+                  "type": "object",
+                  "title": "Additional action data",
+                  "description": "Fixed Home Assistant service data. The selected picker value is merged into this object using the picker's data_attribute. Service-specific fields cannot be schema checked here."
+                },
                 "picker": {
                   "type": "object",
                   "title": "Number picker configuration",