Show notification for launch.json parsing errors

[zeiran]

Good afternoon.

I've noticed that nvim-dap does not display error messages when parsing launch.json, so it's difficult to understand the cause of possible problems.

I suggest adding an error message, in my case it looks like this:

Cannot get configurations from `launch.json`:
...\Local\nvim-data\plugged\nvim-dap/lua/dap/ext/vscode.lua:150: Error parsing launch.json: Expected object key string but found T_OBJ_END at character 1180