update readme

Author: varthe

README.md

@@ -91,6 +91,7 @@ filters:
           contentRatings:
               exclude: [12, 16]
           requestedBy_username: user
+          max_seasons: 2
       apply: radarr_anime
 ```
 

fields.md

@@ -6,6 +6,7 @@ Example values for each field can be found in [filters.test.js](https://github.c
 
 - `requestedBy_email`
 - `requestedBy_username`
+- `max_seasons`
 
 <br />