Initial work on Vision support in text conversations and Image Editing

This is a huge patch which does some major refactoring like:

- renaming "Image Generation" to "Image Creation" in most places,
  to better match its new command (`!bai image create`)

- relocating image creation command (`!bai image` -> `!bai image create`),
  so it wouldn't conflict with the new image editing command (`!bai image edit`)

- introducing a new image editing command (`!bai image edit`), which
  is meant to work only with the OpenAI provider, but doesn't fully work yet
  due to https://github.com/64bit/async-openai/issues/364, though a next patch will fix it

- adding support for reading images off of Matrix conversations and forwarding them to
  text conversations. Works for OpenAI, but not for Anthropic yet
  (requires custom patches) and not for OpenAI-Compat (no support for
  images there)

- relocating some utils around (base64, mime)

docs/features.md

@@ -139,26 +139,42 @@ To operate in this mode, you can:
 - optionally adjust [🦻 Speech-to-Text / 🪄 Message Type for non-threaded only-transcribed messages](./configuration/speech-to-text.md#-message-type-for-non-threaded-only-transcribed-messages), if you'd like to bot to send messages of type `notice` (for better compatibility with other bots in the room) instead of sending regular `text` messages (default)
 
 
-### 🖌️ Image Generation
+### Image Generation
 
-Image generation is the bot's ability to **generate images** based on text prompts.
+#### 🖌️ Image Creation
 
-See a [🖼️ Screenshot of the Image Generation feature](./screenshots/image-generation.webp).
+Image creation is the bot's ability to **create images** based on text prompts.
+
+See a [🖼️ Screenshot of the Image Creation feature](./screenshots/image-creation.webp).
 
 You may also wish to see:
 
 - [🛠️ Configuration / 🖌️ Image Generation](./configuration/image-generation.md) for configuration options related to Image Generation
-- [📖 Usage / 🖌️ Image Generation](./usage.md#-image-generation) section for more details on how to use the bot for Image Generation in a room
-- [🫵 Sticker Generation](#-sticker-generation) - a special case of Image Generation
+- [📖 Usage / Image Generation / 🖌️ Creating Images](./usage.md#-creating-images) section for more details on how to use the bot for Image Creation in a room
+- [🖌️ Image Editing](#️-image-editing) - another image generation feature
+- [🫵 Sticker Creation](#-sticker-creation) - a special case of Image Creation
 
 
-### 🫵 Sticker Generation
+#### 🎨 Image Editing
 
-Sticker generation is the bot's ability to **generate sticker** images based on text prompts. It's a special case of [🖌️ Image Generation](#️-image-generation).
+Image editing is the bot's ability to **edit images** based on a prompt and one or more existing images.
 
-See a [🖼️ Screenshot of the Sticker Generation feature](./screenshots/sticker-generation.webp).
+See a [🖼️ Screenshot of the Image Editing feature](./screenshots/image-editing.webp).
 
-See [📖 Usage / 🖌️ Image Generation / Generating Stickers](./usage.md#generating-stickers) for details.
+You may also wish to see:
+
+- [🛠️ Configuration / 🖌️ Image Generation](./configuration/image-generation.md) for configuration options related to Image Generation
+- [📖 Usage / Image Generation / 🎨 Editing images](./usage.md#-editing-images) section for more details on how to use the bot for Image Editing in a room
+- [🖌️ Image Creation](#️-image-creation) - another image generation feature
+
+
+#### 🫵 Sticker Creation
+
+Sticker generation is the bot's ability to **generate sticker** images based on text prompts. It's a special case of [🖌️ Image Creation](#️-image-creation).
+
+See a [🖼️ Screenshot of the Sticker Creation feature](./screenshots/sticker-generation.webp).
+
+See [📖 Usage / Image Generation / 🫵 Creating Stickers](./usage.md#-creating-stickers) for details.
 
 
 ### 🔒 Encryption