docs(graphql): added filtering section (#110)

(cherry picked from commit b07c916d68)

docs/guide/graphql/filtering/index.md

@@ -6,6 +6,82 @@ title: Filtering
 
 ---
 
-// TODO
+Most queries provide filtering arguments using the AND operator. Filtering arguments are built using `{fields}_{filter}`.
 
-// Note: Waiting API refactor.
+## All Filters
+
+* Eq: `name` (without the filter argument)
+* Like: `name_like`
+* In: `id_in`
+* Not in: `id_not_in`
+* Greater: `id_greater`
+* Lesser: `id_lesser`
+
+Query example:
+```graphql
+query {
+    animes(name_like: "%monogatari%") {
+        data {
+            name
+        }
+    }
+}
+```
+
+## Available Filters for the fields
+
+### String Fields
+
+* Eq
+* Like
+
+### Int Fields
+
+* Eq
+* In
+* Not in
+* Greater
+* Lesser
+
+### Float Fields
+
+* Eq
+* In
+* Not in
+* Lesser
+* Greater
+
+### Boolean Fields
+
+* Eq
+
+### Enum Fields
+
+* Eq
+* In
+* Not in
+
+### DateTimeTz Fields
+
+* Eq
+* Greater
+* Lesser
+
+
+## Nested Filtering
+
+Filtering in relationships is applied **ONLY** on the relationship and it doesn't affect the previous root.
+
+```graphql
+query {
+    animes {
+        data {
+            name
+            animethemes(type: OP) {
+                type
+                sequence
+            }
+        }
+    }
+}
+```