fix: Support numbers as pre release (#943)

Fixes #940

## Description

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## Type of Change

<!--- Put an `x` in all the boxes that apply: -->

- [ ] ✨ `feat` -- New feature (non-breaking change which adds
functionality)
- [x] 🛠️ `fix` -- Bug fix (non-breaking change which fixes an issue)
- [ ] ❌ `!` -- Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] 🧹 `refactor` -- Code refactor
- [ ] ✅ `ci` -- Build configuration change
- [ ] 📝 `docs` -- Documentation
- [ ] 🗑️ `chore` -- Chore

Author: ValentinVignal

packages/melos/lib/src/commands/publish.dart

@@ -150,8 +150,8 @@ mixin _PublishMixin on _ExecMixin {
       // prerelease version with a matching preid instead if any.
       if (package.version.isPreRelease) {
         final preid = package.version.preRelease.length == 4
-            ? package.version.preRelease[2] as String
-            : package.version.preRelease[0] as String;
+            ? package.version.preRelease[2].toString()
+            : package.version.preRelease[0].toString();
         final versionsWithPreid = versions
             .where((version) => version.contains(preid))
             .toList();

packages/melos/test/commands/publish_test.dart

@@ -120,6 +120,38 @@ void main() {
         });
       }
     });
+
+    test('should support number as pre release version', () async {
+      final logger = TestLogger();
+      final workspaceDir = await createTemporaryWorkspace(
+        configBuilder: (path) => MelosWorkspaceConfig(
+          path: path,
+          name: 'test_workspace',
+          packages: [
+            createGlob('packages/**', currentDirectoryPath: path),
+          ],
+        ),
+
+        workspacePackages: const ['a'],
+      );
+
+      await createProject(
+        workspaceDir,
+        Pubspec('a', version: Version(1, 2, 3, pre: '4')),
+      );
+
+      final config = await MelosWorkspaceConfig.fromWorkspaceRoot(
+        workspaceDir,
+      );
+      final melos = Melos(
+        config: config,
+        logger: logger,
+      );
+
+      await expectLater(melos.publish(force: true), completes);
+      final output = logger.output.normalizeLines().split('\n');
+      expect(output, contains('Publishing a 1.2.3-4 to https://pub.dev:'));
+    });
   });
 }