Set the first row as column names for previewing xlsx files

[psychelzh]

Now the first row as column names works for .csv files, but not for .xlsx files. Please let it support .xlsx files. What's more, the color of the first row of .xlsx file previewing sometimes does not agree with the theme color:

[RandomFractals]

@psychelzh try vscode-data-preview instead.

Data Preview ext. provides .xlsx column headers, column selections, sorting, filtering, pivoting, exporting to json, csv, other data formats and charting :)