Add emacs keybindings for mark emulation

These keybindings extend the already selected text. This allows closer
emacs emulation where subsequent movement commands extend / shrink the
current selection instead of dismissing it.

assets/keymaps/linux/emacs.json

@@ -54,6 +54,21 @@
       "alt-^": "editor::JoinLines" // join-line
     }
   },
+  {
+    "context": "Editor && selection",
+    "bindings": {
+      "ctrl-f": "editor::SelectRight",
+      "ctrl-b": "editor::SelectLeft",
+      "ctrl-n": "editor::SelectDown",
+      "ctrl-p": "editor::SelectUp",
+      "ctrl-a": "editor::SelectToBeginningOfLine",
+      "ctrl-e": "editor::SelectToEndOfLine",
+      "alt-f": "editor::SelectToNextWordEnd",
+      "alt-b": "editor::SelectToPreviousSubwordStart",
+      "alt-<": "editor::SelectToBeginning",
+      "alt->": "editor::SelectToEnd"
+    }
+  },
   {
     "context": "Workspace && !Terminal",
     "bindings": {