FEATURE: open multiple files side by side

[ShMcK]

Allow for the extension to load two or more files, possibly in specific configurations.

See VSCode Commands under setEditorLayout

vscode.setEditorLayout - Sets the editor layout.

layout - The editor layout to set.
The layout is described as object with an initial (optional) orientation (0 = horizontal, 1 = vertical) and an array of editor groups within.
Each editor group can have a size and another array of editor groups that will be laid out orthogonal to the orientation.
If editor group sizes are provided, their sum must be 1 to be applied per row or column.
Example for a 2x2 grid: { orientation: 0, groups: [{ groups: [{}, {}], size: 0.5 }, { groups: [{}, {}], size: 0.5 }] }