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/agents.md

@@ -35,7 +35,7 @@ Depending on where the agent is defined (within a room, globally, or [statically
 
 When creating an agent, you will be given some sample [YAML](https://en.wikipedia.org/wiki/YAML) configuration which you can use to customize the agent's behavior.
 
-This configuration varies depending on the [☁️ provider](./providers.md) used and the capabilities of the agent. Based on the configuration keys you pass, certain features will be enabled or disabled. For example, if you skip the `image_generation` key for an [OpenAI](./providers.md#openai) agent, it won't be able to generate images (see [🖌️ Image Generation](./features.md#-image-generation)).
+This configuration varies depending on the [☁️ provider](./providers.md) used and the capabilities of the agent. Based on the configuration keys you pass, certain features will be enabled or disabled. For example, if you skip the `image_generation` key for an [OpenAI](./providers.md#openai) agent, it won't be able to generate images (see [🖌️ Image Creation](./features.md#-image-creation), [🎨 Image Editing](./features.md#-image-editing), [🫵 Sticker Creation](./features.md#-sticker-creation)).
 
 After making your modifications to the sample YAML, you submit it back to the bot and the new agent will be created.