add a nix package (with CI tests) for libghostty-vt (#12090)

.github/workflows/test.yml

@@ -653,6 +653,18 @@ jobs:
       - name: Check to see if the binary has not been stripped
         run: nm result/bin/.ghostty-wrapped 2>&1 | grep -q 'main_ghostty.main'
 
+      - name: Test ReleaseFast build of libghostty-vt
+        run: nix build .#libghostty-vt-releasefast
+
+      - name: Check to see if the library looks sane
+        run: nm result/lib/libghostty-vt.so.0.1.0 2>&1 | grep -q 'ghostty_terminal_new'
+
+      - name: Test Debug build of libghostty-vt
+        run: nix build .#libghostty-vt-debug
+
+      - name: Check to see if the library looks sane
+        run: nm result/lib/libghostty-vt.so.0.1.0 2>&1 | grep -q 'ghostty_terminal_new'
+
   build-dist:
     runs-on: namespace-profile-ghostty-sm
     needs: test