Display metadata #14

There are information about the file that could be relevant to the user.

Global information
This could be added in a row above the table.

• Number of rows/columns (not immediately available without scrolling)
• Size of file

Column level information
This could be added under the column name, or on hover

• Type of the column data type (string, int, categorical... nullable?)
• Easily available statistics, for instance for Parquet we may get for free min, max, null count, sometimes distinct count
• Optionally, we could compute other statistics (more expensive) on demand: mean/media/stddev distribution...