Incorrect nested header - colspan vaue not correct

[ecofi]

Describe the bug
If the parent column includes only one child column and the child columns includes multiple columns, the header of the parent column is incorrect. I did not test if other scenarios are possible also resulting in incorrect colspan value and might be assesses in fixing the issue.

To Reproduce
Steps to reproduce the behavior:
This is an example, modified from example page here: https://gridjs.io/docs/examples/nested-header
const grid = new Grid({ columns: [ { name: 'Test', columns:[ { name: 'Name', columns: [{ name: 'First' }, { name: 'Last' }] } ] } ], data: Array(50).fill().map(x => [ faker.name.firstName(), faker.name.lastName(), faker.internet.email(), ]) });

The parent column header "Test" does not cover the full table.

Expected behavior
In the above example, the parent column header "Test" should span across the full table

Screenshots
See attached screenshot

Additional context
I really like the nested header feature.

I updated the initial post with an better example