chore: move single file to own folder (#1030)

See https://github.com/CLIUtils/CLI11/pull/1025.

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

.github/workflows/build.yml

@@ -36,13 +36,10 @@ jobs:
       - name: Make header
         run: cmake --build build --target CLI11-generate-single-file
 
-      - name: Copy file to main folder
-        run: cp build/include/CLI11.hpp CLI11.hpp
-
       - uses: actions/upload-artifact@v4
         with:
           name: CLI11.hpp
-          path: CLI11.hpp
+          path: build/single-include/CLI11.hpp
 
       - uses: actions/upload-artifact@v4
         with:
@@ -54,6 +51,4 @@ jobs:
         if: startsWith(github.ref, 'refs/tags/')
         with:
           files: |
-            CLI11.hpp
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+            build/single-include/CLI11.hpp