Formatter should handle [{...}] better

[huggsboson]

jsonnet fmt changed the following code from:

                        volumeMounts: [
                            {
                                name: "deployment-config",
                                mountPath:
                                    if cluster.isLocal then
                                        "/box/deployment-config"
                                    else
                                        "/box"
                                ,
                            },
                        ],

to:

                        volumeMounts: [
                            {
                                name: "deployment-config",
                                mountPath:
                                    if cluster.isLocal then
                                        "/box/deployment-config"
                                    else
                                        "/box",
                                },
                        ],

which is mis-indented. My personal taste would have had the whole thing turned to:

                        volumeMounts: [{
                            name: "deployment-config",
                            mountPath:
                                if cluster.isLocal then
                                    "/box/deployment-config"
                                else
                                    "/box",
                        }],

[sparkprime]

#231 should fix the first issue

As for [{...}] it will already preserve that style, but actually enforcing the style is a feature request. As for the actual logic, I suppose you're asking for the newlines to be removed for single element arrays of the form [ expr (optional comma) ]
It's quite easy to write a pass in formatter.cpp to implement that.