Add TShock.Installer to download dotnet runtime

This will include a new ./TShock.Installer executable that will be for users without the dotnet runtime. This program will download the dotnet runtime, extract it, and then run ./TShock.Server for them using the downloaded runtime.

Note: only tested on osx, likely a no-go for linux/windows until more testing occurs.

.github/workflows/ci-otapi3.yml

@@ -36,6 +36,11 @@ jobs:
       - name: Install msgfmt
         run: sudo apt-get install -y gettext
 
+      - name: Produce installer
+        run: |
+            cd TShockInstaller
+            dotnet publish -r ${{ matrix.arch }} -f net6.0 -c Release -p:PublishSingleFile=true --self-contained true
+
       - name: Produce build
         run: |
             cd TShockLauncher
@@ -46,6 +51,10 @@ jobs:
         run: |
             chmod +x TShockLauncher/bin/Release/net6.0/${{ matrix.arch }}/publish/TShock.Server
 
+      - name: Copy installer
+        run: |
+            cp TShockInstaller/bin/Release/net6.0/${{ matrix.arch }}/publish/* TShockLauncher/bin/Release/net6.0/${{ matrix.arch }}/publish/
+
       # preserve file perms: https://github.com/actions/upload-artifact#maintaining-file-permissions-and-case-sensitive-files
       - name: Tarball artifact (non-Windows)
         if: ${{ matrix.arch != 'win-x64' }}