feat: implement update an issue comment

lib/src/common/github.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 import 'dart:convert';
+
 import 'package:github/src/common.dart';
 import 'package:github/src/common/util/utils.dart';
 import 'package:http/http.dart' as http;
@@ -245,6 +246,48 @@ class GitHub {
         preview: preview,
       );
 
+  /// Handles PATCH Requests that respond with JSON
+  ///
+  /// [path] can either be a path like '/repos' or a full url.
+  /// [statusCode] is the expected status code. If it is null, it is ignored.
+  /// If the status code that the response returns is not the status code you provide
+  /// then the [fail] function will be called with the HTTP Response.
+  ///
+  /// If you don't throw an error or break out somehow, it will go into some error checking
+  /// that throws exceptions when it finds a 404 or 401. If it doesn't find a general HTTP Status Code
+  /// for errors, it throws an Unknown Error.
+  ///
+  /// [headers] are HTTP Headers. If it doesn't exist, the 'Accept' and 'Authorization' headers are added.
+  /// [params] are query string parameters.
+  /// [convert] is a simple function that is passed this [GitHub] instance and a JSON object.
+  ///
+  /// The future will pass the object returned from this function to the then method.
+  /// The default [convert] function returns the input object.
+  /// [body] is the data to send to the server. Pass in a List<int> if you want to post binary body data. Everything else will have .toString() called on it and set as text content
+  /// [S] represents the input type.
+  /// [T] represents the type return from this function after conversion
+  Future<T> patchJSON<S, T>(
+    String path, {
+    int? statusCode,
+    void Function(http.Response response)? fail,
+    Map<String, String>? headers,
+    Map<String, dynamic>? params,
+    JSONConverter<S, T>? convert,
+    dynamic body,
+    String? preview,
+  }) =>
+      requestJson(
+        'PATCH',
+        path,
+        statusCode: statusCode,
+        fail: fail,
+        headers: headers,
+        params: params,
+        convert: convert,
+        body: body,
+        preview: preview,
+      );
+
   Future<T> requestJson<S, T>(
     String method,
     String path, {

lib/src/common/issues_service.dart

@@ -251,7 +251,18 @@ class IssuesService extends Service {
     );
   }
 
-  // TODO: Implement editComment: https://developer.github.com/v3/issues/comments/#edit-a-comment
+  /// Update an issue comment.
+  ///
+  /// API docs: https://docs.github.com/en/rest/reference/issues#update-an-issue-comment
+  Future<IssueComment> updateComment(RepositorySlug slug, int id, String body) {
+    final it = GitHubJson.encode({'body': body});
+    return github.postJSON(
+      '/repos/${slug.fullName}/issues/comments/$id',
+      body: it,
+      convert: (dynamic i) => IssueComment.fromJson(i),
+      statusCode: StatusCodes.OK,
+    );
+  }
 
   /// Deletes an issue comment.
   ///