Documented more public symbols

Sources/Turf/Feature.swift

@@ -7,10 +7,24 @@ import CoreLocation
  A [Feature object](https://datatracker.ietf.org/doc/html/rfc7946#section-3.2) represents a spatially bounded thing.
  */
 public struct Feature: Equatable {
+    /**
+     A string or number that commonly identifies the feature in the context of a data set.
+
+     Turf does not guarantee that the feature is unique; however, a data set may make such a guarantee.
+     */
     public var identifier: FeatureIdentifier?
+
+    /// Arbitrary, JSON-compatible attributes to associate with the feature.
     public var properties: JSONObject?
+
+    /// The geometry at which the feature is located.
     public var geometry: Geometry?
 
+    /**
+     Initializes a feature located at the given geometry.
+
+     - parameter geometry: The geometry at which the feature is located.
+     */
     public init(geometry: Geometry?) {
         self.geometry = geometry
     }

Sources/Turf/FeatureCollection.swift

@@ -4,8 +4,14 @@ import Foundation
  A [FeatureCollection object](https://datatracker.ietf.org/doc/html/rfc7946#section-3.3) is a collection of Feature objects.
  */
 public struct FeatureCollection: Equatable {
-    public var features: Array<Feature> = []
+    /// The features that the collection contains.
+    public var features: [Feature] = []
 
+    /**
+     Initializes a feature collection containing the given features.
+
+     - parameter features: The features that the collection contains.
+     */
     public init(features: [Feature]) {
         self.features = features
     }

Sources/Turf/Geometries/MultiPolygon.swift

@@ -10,6 +10,13 @@ public struct MultiPolygon: Equatable {
     /// The positions at which the multipolygon is located. Each nested array corresponds to one polygon.
     public var coordinates: [[[LocationCoordinate2D]]]
 
+    /// The polygon geometries that conceptually form the multipolygon.
+    public var polygons: [Polygon] {
+        return coordinates.map { (coordinates) -> Polygon in
+            return Polygon(coordinates)
+        }
+    }
+
     /**
      Initializes a multipolygon defined by the given positions.
 
@@ -56,13 +63,6 @@ extension MultiPolygon: Codable {
 }
 
 extension MultiPolygon {
-
-    public var polygons: [Polygon] {
-        return coordinates.map { (coordinates) -> Polygon in
-            return Polygon(coordinates)
-        }
-    }
-
     /**
      * Determines if the given coordinate falls within any of the polygons.
      * The optional parameter `ignoreBoundary` will result in the method returning true if the given coordinate

Sources/Turf/RadianCoordinate2D.swift

@@ -3,22 +3,38 @@ import Foundation
 import CoreLocation
 #endif
 
+/// A latitude or longitude measured in radians, as opposed to `LocationDegrees`, which is measured in degrees of arc.
 public typealias LocationRadians = Double
+
+/// A difference in latitude or longitude measured in radians, as opposed to `CLLocationDegrees`, which is used by some libraries to represent a similar distance measured in degrees of arc.
 public typealias RadianDistance = Double
 
 /**
- A `RadianCoordinate2D` is a coordinate represented in radians as opposed to
- `LocationCoordinate2D` which is represented in latitude and longitude.
+ A coordinate pair measured in radians, as opposed to `LocationCoordinate2D`, which is measured in degrees of arc.
  */
 public struct RadianCoordinate2D {
+    /// The latitude measured in radians.
     private(set) var latitude: LocationRadians
+
+    /// The longitude measured in radians.
     private(set) var longitude: LocationRadians
 
+    /**
+     Initializes a coordinate pair located at the given latitude and longitude.
+
+     - parameter latitude: The latitude measured in radians.
+     - parameter longitude: The longitude measured in radians.
+     */
     public init(latitude: LocationRadians, longitude: LocationRadians) {
         self.latitude = latitude
         self.longitude = longitude
     }
 
+    /**
+     Initializes a coordinate pair measured in radians that is coincident to the given coordinate pair measured in degrees of arc.
+
+     - parameter degreeCoordinate: A coordinate pair measured in degrees of arc.
+     */
     public init(_ degreeCoordinate: LocationCoordinate2D) {
         latitude = degreeCoordinate.latitude.toRadians()
         longitude = degreeCoordinate.longitude.toRadians()