Run initializeCommand for `devcontainer build`

### When
```sh
$ devcontainer build --workspace-folder .
```

### Expected
By default, things like `initialcommand` are called.

### Actual
Things like `initialcommand` are not called.

### Feat
All default things vscode devcontainer does, like `xxxcommand` , extensions, cwd...

```sh
$ ls .devcontainer/devcontainer.json
.devcontainer/devcontainer.json
$ devcontainer vscode build
Run initialcommand
...
Start: Run: docker build
Step 1: FROM
Step 2: RUN xxx
Step 3: RUN xxx
...
```