feat: Add Chat Trigger node (#7409)

Signed-off-by: Oleg Ivaniv <me@olegivaniv.com>
Co-authored-by: Jan Oberhauser <jan.oberhauser@gmail.com>
Co-authored-by: Jesper Bylund <mail@jesperbylund.com>
Co-authored-by: OlegIvaniv <me@olegivaniv.com>
Co-authored-by: Deborah <deborah@starfallprojects.co.uk>
Co-authored-by: Jan Oberhauser <janober@users.noreply.github.com>
Co-authored-by: Jon <jonathan.bennetts@gmail.com>
Co-authored-by: कारतोफ्फेलस्क्रिप्ट™ <aditya@netroy.in>
Co-authored-by: Michael Kret <88898367+michael-radency@users.noreply.github.com>
Co-authored-by: Giulio Andreini <andreini@netseven.it>
Co-authored-by: Mason Geloso <Mason.geloso@gmail.com>
Co-authored-by: Mason Geloso <hone@Masons-Mac-mini.local>
Co-authored-by: Mutasem Aldmour <mutasem@n8n.io>

packages/@n8n/nodes-langchain/nodes/chains/ChainLLM/ChainLlm.node.ts

@@ -217,7 +217,7 @@ export class ChainLlm implements INodeType {
 		name: 'chainLlm',
 		icon: 'fa:link',
 		group: ['transform'],
-		version: [1, 1.1, 1.2],
+		version: [1, 1.1, 1.2, 1.3],
 		description: 'A simple chain to prompt a large language model',
 		defaults: {
 			name: 'Basic LLM Chain',
@@ -266,6 +266,18 @@ export class ChainLlm implements INodeType {
 					},
 				},
 			},
+			{
+				displayName: 'Prompt',
+				name: 'prompt',
+				type: 'string',
+				required: true,
+				default: '={{ $json.chatInput }}',
+				displayOptions: {
+					show: {
+						'@version': [1.3],
+					},
+				},
+			},
 			{
 				displayName: 'Chat Messages (if Using a Chat Model)',
 				name: 'messages',