Add tablet option map-to-focused-output

docs/wiki/Configuration:-Input.md

@@ -89,6 +89,7 @@ input {
     tablet {
         // off
         map-to-output "eDP-1"
+        // map-to-focused-output
         // left-handed
         // calibration-matrix 1.0 0.0 0.0 0.0 1.0 0.0
     }
@@ -281,6 +282,10 @@ Valid output names are the same as the ones used for output configuration.
 
 <sup>Since: 0.1.7</sup> When a tablet is not mapped to any output, it will map to the union of all connected outputs, without aspect ratio correction.
 
+Setting specific to `tablet`:
+
+- `map-to-focused-output`: <sup>Since: next release</sup> will map the tablet to the focused output, takes precedence over `map-to-output`.
+
 ### General Settings
 
 These settings are not specific to a particular input device.