Clarify .env.template image-provider options (Significant-Gravitas#3720)

* Clarify .env.template image-provider options

* feat: consolidate duplicate options

* Simplify

---------

Co-authored-by: Nicholas Tindle <nicktindle@outlook.com>
Co-authored-by: Nicholas Tindle <nick@ntindle.com>
Co-authored-by: k-boikov <64261260+k-boikov@users.noreply.github.com>

.env.template

@@ -149,10 +149,10 @@ OPENAI_API_KEY=your-openai-api-key
 ### IMAGE GENERATION PROVIDER
 ################################################################################
 
-### OPEN AI
-## IMAGE_PROVIDER - Image provider (Example: dalle)
+### COMMON SETTINGS
+## IMAGE_PROVIDER - Image provider - dalle, huggingface, or sdwebui
 ## IMAGE_SIZE - Image size (Example: 256)
-##   DALLE: 256, 512, 1024
+## Image sizes for dalle: 256, 512, 1024
 # IMAGE_PROVIDER=dalle
 # IMAGE_SIZE=256