Add devcontainer config for developing Gitea (#24781)

With the recent release of https://github.com/loft-sh/devpod making
ephemeral dev environments (ala GitPod/Codespaces) much easier (aka, no
pre-configured infra required). This allows an alternative to using
GitPod for such development options.

---------

Co-authored-by: Yarden Shoham <git@yardenshoham.com>
Co-authored-by: Giteabot <teabot@gitea.io>

.devcontainer/devcontainer.json

@@ -0,0 +1,34 @@
+{
+  "name": "Gitea DevContainer",
+  "image": "mcr.microsoft.com/devcontainers/go:1.20",
+  "features": {
+    // installs nodejs into container
+    "ghcr.io/devcontainers/features/node:1": {
+      "version":"20"
+    }
+  },
+  "customizations": {
+    "vscode": {
+      "settings": {},
+      // same extensions as Gitpod, should match /.gitpod.yml
+      "extensions": [
+        "editorconfig.editorconfig",
+        "dbaeumer.vscode-eslint",
+        "golang.go",
+        "stylelint.vscode-stylelint",
+        "DavidAnson.vscode-markdownlint",
+        "Vue.volar",
+        "ms-azuretools.vscode-docker",
+        "zixuanchen.vitest-explorer",
+        "alexcvzz.vscode-sqlite"
+      ]
+    }
+  },
+  "portsAttributes": {
+    "3000": {
+      "label": "Gitea Web",
+      "onAutoForward": "notify"
+    }
+  },
+  "postCreateCommand": "make deps"
+}