feature: add on-demand vrr (#586)

* feature: add on-demand vrr

* Don't require connector::Info in try_to_set_vrr

* Improve VRR help message

* Rename connector_handle => connector

* Fix tracy span name

* Move on demand vrr flag set higher

* wiki: Mention on-demand VRR

---------

Co-authored-by: Ivan Molodetskikh <yalterz@gmail.com>

wiki/Configuration:-Window-Rules.md

@@ -47,6 +47,7 @@ window-rule {
     opacity 0.5
     block-out-from "screencast"
     // block-out-from "screen-capture"
+    variable-refresh-rate true
 
     focus-ring {
         // off
@@ -391,6 +392,26 @@ window-rule {
 }
 ```
 
+#### `variable-refresh-rate`
+
+<sup>Since: 0.1.9</sup>
+
+If set to true, whenever this window displays on an output with on-demand VRR, it will enable VRR on that output.
+
+```kdl
+// Configure some output with on-demand VRR.
+output "HDMI-A-1" {
+    variable-refresh-rate on-demand=true
+}
+
+// Enable on-demand VRR when mpv displays on the output.
+window-rule {
+    match app-id="^mpv$"
+
+    variable-refresh-rate true
+}
+```
+
 #### `draw-border-with-background`
 
 Override whether the border and the focus ring draw with a background.