Add support for DreamGen API.

API docs: https://dreamgen.com/docs/models/opus/v1
API keys: https://dreamgen.com/account/api-keys

I decided to base this on the text-completion API since it's more
flexible with SillyTavern's prompt formating capabilities.

This also means that custom context and instruct settings are required.

Will add documentation in a followup PR.

src/constants.js

@@ -177,6 +177,7 @@ const TEXTGEN_TYPES = {
     LLAMACPP: 'llamacpp',
     OLLAMA: 'ollama',
     INFERMATICAI: 'infermaticai',
+    DREAMGEN: 'dreamgen',
     OPENROUTER: 'openrouter',
 };
 
@@ -192,6 +193,22 @@ const INFERMATICAI_KEYS = [
     'stop',
 ];
 
+// https://dreamgen.com/docs/api#openai-text
+const DREAMGEN_KEYS = [
+    'model',
+    'prompt',
+    'max_tokens',
+    'temperature',
+    'top_p',
+    'top_k',
+    'min_p',
+    'repetition_penalty',
+    'frequency_penalty',
+    'presence_penalty',
+    'stop',
+    'minimum_message_content_tokens'
+];
+
 // https://docs.together.ai/reference/completions
 const TOGETHERAI_KEYS = [
     'model',
@@ -263,6 +280,7 @@ module.exports = {
     TOGETHERAI_KEYS,
     OLLAMA_KEYS,
     INFERMATICAI_KEYS,
+    DREAMGEN_KEYS,
     OPENROUTER_HEADERS,
     OPENROUTER_KEYS,
 };