add phase_angle to ledc component (#3671)

components/output/ledc.rst

@@ -83,6 +83,11 @@ channel 0, 2, 4, 6 for each output. This will prevent issues that arise from aut
 which chooses adjacent channels with shared timers. See
 `Issue #3114 <https://github.com/esphome/issues/issues/3114>`__ for more details.
 
+- **phase_angle** (*Optional*, float): Set a phase angle to the other channel of this timer.
+  Range 0-360°, defaults to 0°
+
+Note: this variable is only available for the esp-idf framework
+
 Recommended frequencies
 -----------------------