Sorting by date string does not result in expected sort order.

[ghing]

Describe the bug

Sorting by a "YYYY-MM-DD" date string does not sort the data in the expected sort order and is not consistent with sorting of those strings using Array.prototype.sort().

To Reproduce

In a Node.js REPL:

const dfd = require('danfojs-node');
const data = {
  date: [ '1974-02-19', '1955-12-06', '1963-11-18' ]
};
const df = new dfd.DataFrame(data);
df.sort_values({by: 'date'}).print();

Expected behavior

This table will be output:

	date
0	1955-12-06
1	1963-11-18
2	1974-02-19

Observed behavior

This table is output

	date
0	1974-02-19
1	1955-12-06
2	1963-11-18

Screenshots

N/A This is running in a Node.js REPL on MacOS 10.15.7.

Additional context

• Node Version: 16.13.0
• Danfo version: 0.3.2