chore: Editor 'plugin' -> 'extension'

They've always been called extensions, not sure why the folder was plugins. Part of ongoing spring cleaning

shared/editor/extensions/Keys.ts

@@ -0,0 +1,99 @@
+import { GapCursor } from "prosemirror-gapcursor";
+import {
+  Plugin,
+  Selection,
+  AllSelection,
+  TextSelection,
+  EditorState,
+} from "prosemirror-state";
+import Extension, { Command } from "../lib/Extension";
+import isInCode from "../queries/isInCode";
+
+export default class Keys extends Extension {
+  get name() {
+    return "keys";
+  }
+
+  keys(): Record<string, Command> {
+    const onCancel = () => {
+      if (this.editor.props.onCancel) {
+        this.editor.props.onCancel();
+        return true;
+      }
+      return false;
+    };
+
+    return {
+      // Shortcuts for when editor has separate edit mode
+      "Mod-Escape": onCancel,
+      "Shift-Escape": onCancel,
+      "Mod-s": () => {
+        if (this.editor.props.onSave) {
+          this.editor.props.onSave({ done: false });
+          return true;
+        }
+        return false;
+      },
+      "Mod-Enter": (state: EditorState) => {
+        if (!isInCode(state) && this.editor.props.onSave) {
+          this.editor.props.onSave({ done: true });
+          return true;
+        }
+        return false;
+      },
+      Escape: () => {
+        (this.editor.view.dom as HTMLElement).blur();
+        return true;
+      },
+    };
+  }
+
+  get plugins() {
+    return [
+      new Plugin({
+        props: {
+          // we can't use the keys bindings for this as we want to preventDefault
+          // on the original keyboard event when handled
+          handleKeyDown: (view, event) => {
+            if (view.state.selection instanceof AllSelection) {
+              if (event.key === "ArrowUp") {
+                const selection = Selection.atStart(view.state.doc);
+                view.dispatch(view.state.tr.setSelection(selection));
+                return true;
+              }
+              if (event.key === "ArrowDown") {
+                const selection = Selection.atEnd(view.state.doc);
+                view.dispatch(view.state.tr.setSelection(selection));
+                return true;
+              }
+            }
+
+            // edge case where horizontal gap cursor does nothing if Enter key
+            // is pressed. Insert a newline and then move the cursor into it.
+            if (view.state.selection instanceof GapCursor) {
+              if (event.key === "Enter") {
+                view.dispatch(
+                  view.state.tr.insert(
+                    view.state.selection.from,
+                    view.state.schema.nodes.paragraph.create({})
+                  )
+                );
+                view.dispatch(
+                  view.state.tr.setSelection(
+                    TextSelection.near(
+                      view.state.doc.resolve(view.state.selection.from),
+                      -1
+                    )
+                  )
+                );
+                return true;
+              }
+            }
+
+            return false;
+          },
+        },
+      }),
+    ];
+  }
+}