Created Extensions (markdown)

Extensions.md

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+# Using extensions
+
+Extensions are a more convenient form of user scripts.
+
+Extensions all exist in their own subdirectory inside the `extensions` directory. You can use git to install an extension like this:
+
+```
+git clone https://github.com/AUTOMATIC1111/stable-diffusion-webui-aesthetic-gradients extensions/aesthetic-gradients
+```
+
+This installs an extension from `https://github.com/AUTOMATIC1111/stable-diffusion-webui-aesthetic-gradients` into the `extensions/aesthetic-gradients` directory.
+
+# Developing extensions
+
+Web ui interacts with installed extensions in the following way:
+- extension's scripts in the `scripts` directory are executed as if they were just usual user scripts, except:
+  - `sys.path` is extended to include the extension directory, so you can import anything in it without worrying
+  - you can use `scripts.basedir()` to get the current extension's directory (since user can name it anything he wants)
+- extension's javascript files in the `javascript` directory are added to the page
+- extension's `style.css` file is added to the page
+