Change panel location of viewsContainers to align to vscode.

[shuyaqian]

Signed-off-by: shuyaqian [email protected]

What it does

Change panel location of viewsContainers to align to vscode.

How to test

Develop a plugin with viewsContainers like:

"viewsContainers": {
	"panel": [
		{
			"id": "package-explorer",
			"title": "Package Explorer",
			"icon": "media/dep.svg"
		}
	]
}

In vscode, this panel will be located in bottom.
But in theia, this panel will be located in left.

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[vince-fugnitto]

The changes look good to me 👍
I confirmed with a customized version of tree-view-sample that the tree-view is added to the bottom panel in the case of panel similarly to vscode.