fix(settings): accept numeric environment booleans

src/settings/mod.rs

@@ -47,7 +47,7 @@ where
         type Value = bool;
 
         fn expecting(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            formatter.write_str("a boolean or a UCI-compatible boolean string")
+            formatter.write_str("a boolean, integer 0 or 1, or a UCI-compatible boolean string")
         }
 
         fn visit_bool<E>(self, value: bool) -> Result<Self::Value, E>
@@ -57,6 +57,28 @@ where
             Ok(value)
         }
 
+        fn visit_i64<E>(self, value: i64) -> Result<Self::Value, E>
+        where
+            E: de::Error,
+        {
+            match value {
+                0 => Ok(false),
+                1 => Ok(true),
+                _ => Err(E::custom("boolean integer must be 0 or 1")),
+            }
+        }
+
+        fn visit_u64<E>(self, value: u64) -> Result<Self::Value, E>
+        where
+            E: de::Error,
+        {
+            match value {
+                0 => Ok(false),
+                1 => Ok(true),
+                _ => Err(E::custom("boolean integer must be 0 or 1")),
+            }
+        }
+
         fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
         where
             E: de::Error,