Make the package not depend directly on package:charcode. (dart-archive/convert#35)

* Make the package not depend directly on package:charcode.

The charcode package is still used a dev-dependency,
but that does not affect users of the convert package.

Author: lrhn

pkgs/convert/lib/src/charcodes.dart

@@ -0,0 +1,36 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Character `%`.
+const int $percent = 0x25;
+
+/// Character `-`.
+const int $dash = 0x2d;
+
+/// Character `.`.
+const int $dot = 0x2e;
+
+/// Character `0`.
+const int $0 = 0x30;
+
+/// Character `9`.
+const int $9 = 0x39;
+
+/// Character `A`.
+const int $A = 0x41;
+
+/// Character `_`.
+const int $underscore = 0x5f;
+
+/// Character `a`.
+const int $a = 0x61;
+
+/// Character `f`.
+const int $f = 0x66;
+
+/// Character `z`.
+const int $z = 0x7a;
+
+/// Character `~`.
+const int $tilde = 0x7e;

pkgs/convert/lib/src/hex/encoder.dart

@@ -7,7 +7,7 @@ library convert.hex.encoder;
 import 'dart:convert';
 import 'dart:typed_data';
 
-import 'package:charcode/ascii.dart';
+import '../charcodes.dart';
 
 /// The canonical instance of [HexEncoder].
 const hexEncoder = HexEncoder._();

pkgs/convert/lib/src/percent/decoder.dart

@@ -6,9 +6,9 @@ library convert.percent.decoder;
 
 import 'dart:convert';
 
-import 'package:charcode/ascii.dart';
 import 'package:typed_data/typed_data.dart';
 
+import '../charcodes.dart';
 import '../utils.dart';
 
 /// The canonical instance of [PercentDecoder].

pkgs/convert/lib/src/percent/encoder.dart

@@ -6,7 +6,7 @@ library convert.percent.encoder;
 
 import 'dart:convert';
 
-import 'package:charcode/ascii.dart';
+import '../charcodes.dart';
 
 /// The canonical instance of [PercentEncoder].
 const percentEncoder = PercentEncoder._();

pkgs/convert/lib/src/utils.dart

@@ -4,7 +4,7 @@
 
 library convert.utils;
 
-import 'package:charcode/ascii.dart';
+import 'charcodes.dart';
 
 /// Returns the digit (0 through 15) corresponding to the hexadecimal code unit
 /// at index [i] in [codeUnits].

pkgs/convert/pubspec.yaml

@@ -7,9 +7,9 @@ environment:
   sdk: '>=2.12.0-0 <3.0.0'
 
 dependencies:
-  charcode: ^1.2.0-nullsafety.3
   typed_data: ^1.3.0-nullsafety.5
 
 dev_dependencies:
+  charcode: ^1.2.0-nullsafety.3
   pedantic: ^1.10.0-nullsafety.3
   test: ^1.16.0-nullsafety.9