objed: add a manual actiation flag

Setting the flag `+manual` of the `objed` module makes the user
responsible for calling `objed-activate` when needed. The binding
`M-SPC` is set in the default Emacs bindings.

modules/editor/objed/README.org

@@ -2,6 +2,11 @@
 #+DATE:    May 30, 2019
 #+SINCE:   v2.1
 
+* Table of Contents :TOC_3:noexport:
+- [[#description][Description]]
+  - [[#module-flags][Module Flags]]
+
+* Description
 This modules adds [[https://github.com/clemera/objed][objed]], a global minor-mode for navigating and manipulating
 text objects. It combines the ideas of versor-mode and other editors like Vim or
 Kakoune and tries to align them with regular Emacs conventions.
@@ -11,3 +16,7 @@ prefer standard Emacs key-bindings and conventions. It's not recommended to use
 these modules together.
 
 [[https://github.com/clemera/objed][See the objed project README]] for information on keybinds and usage.
+
+** Module Flags
++ ~+manual~ Do not turn =objed= automatically. The user is responsible for calling
+  `objed-activate` (bound to `M-SPC` if using the default Emacs bindings.)

modules/editor/objed/config.el

@@ -27,4 +27,5 @@
   (advice-add 'objed--init :after #'+objed*add-face-remaps)
   (advice-add 'objed--reset :after #'+objed*remove-face-remaps)
 
-  (objed-mode +1))
+  (unless (featurep! +manual)
+    (objed-mode +1)))