Update devcontainer

.devcontainer/all/Dockerfile

@@ -39,3 +39,5 @@ RUN cd ~ && git clone --depth 1 'https://git.ffmpeg.org/ffmpeg.git' && cd ffmpeg
 RUN curl https://sh.rustup.rs -sSf | \
     sh -s -- --default-toolchain nightly -y
 ENV PATH=/root/.cargo/bin:$PATH
+# Enable GPG sign by default
+RUN git config commit.gpgsign true

.devcontainer/all/devcontainer.json

@@ -4,9 +4,7 @@
         "dockerfile": "Dockerfile"
     },
     "extensions": [
-        "rust-lang.rust-analyzer",
-        "GitHub.copilot",
-        "ms-vscode.hexeditor"
+        "rust-lang.rust-analyzer"
     ],
     "settings": {
         "rust-analyzer.cargo.features": [
@@ -24,5 +22,6 @@
                 }
             }
         }
-    }
+    },
+    "postCreateCommand": "cd /workspaces/pixiv_downloader && git submodule update --init"
 }