fix: clean slate from v0.3.0

- csproj: revert to 0.3.0
- package-velopack.ps1: clean output dir before vpk pack, keep feed files (json/nupkg) for GiteaSource auto-update
- ci.yml: upload feed files (json/nupkg) to Gitea release for GiteaSource auto-update

.gitea/workflows/ci.yml

@@ -162,6 +162,8 @@ jobs:
           files: |
             artifacts/velopack/win-x64-stable/*.exe
             artifacts/velopack/win-x64-stable/*.zip
+            artifacts/velopack/win-x64-stable/*.json
+            artifacts/velopack/win-x64-stable/*.nupkg
           name: ${{ gitea.ref_name }}
           body: |
             Release ${{ gitea.ref_name }}