Adding lockbindings option for disallowing lua to modify bindings at all

runtime/help/options.md

@@ -231,6 +231,12 @@ Here are the available options:
 
     default value: `false`
 
+* `lockbindings`: prevent plugins and lua scripts from binding any keys.
+   Any custom actions must be binded manually either via commands like `bind`
+   or by modifying the `bindings.json` file.
+
+    default value: `false`
+
 * `matchbrace`: show matching braces for '()', '{}', '[]' when the cursor
    is on a brace character or (if `matchbraceleft` is enabled) next to it.
 

runtime/help/plugins.md

@@ -178,6 +178,8 @@ The packages and their contents are listed below (in Go type signatures):
        bind the key `k` to the string `v`. If `overwrite` is true, this will
        overwrite any existing binding to key `k`.
        Returns true if the binding was made, and a possible error.
+       This operation can be rejected by `lockbindings` to prevent undesired
+       actions by the user.
 
     - `Reload()`: reload configuration files.