Add PasteEditProvider (#107283)

For #30066

This adds a new `documentPaste` api proposal that lets extensions hook into copy and paste.

This can be used to do things such as:

- Create link when pasting an image
- Bring along imports when copy and pasting code

extensions/markdown-language-features/package.json

@@ -16,7 +16,8 @@
     "Programming Languages"
   ],
   "enabledApiProposals": [
-    "textEditorDrop"
+    "textEditorDrop",
+    "documentPaste"
   ],
   "activationEvents": [
     "onLanguage:markdown",
@@ -414,6 +415,12 @@
           "markdownDescription": "%configuration.markdown.editor.drop.enabled%",
           "scope": "resource"
         },
+        "markdown.experimental.editor.pasteLinks.enabled": {
+          "type": "boolean",
+          "default": false,
+          "markdownDescription": "%configuration.markdown.editor.pasteLinks.enabled%",
+          "scope": "resource"
+        },
         "markdown.experimental.validate.enabled": {
           "type": "boolean",
           "scope": "resource",