docs: added interpolation options to manpage

manpages/hinoirisetr.1.md

@@ -63,7 +63,13 @@ If not found, the daemon emits a warning and uses built-in defaults.
 
 ## Section `[time]`
 
-All values in hours (0–23):
+Interpolation options:
+
+- interpolation_temp
+- interpolation_gamma
+  available options: linear, cubic, cubiceaseinout, cosine, exponential
+
+Values in hours (0–23):
 
 - **sunset_start**
 - **sunset_end**