Describe the bug

PR #5746 added a sortKey field option. The typescript type definition was incorrectly updated to add this as a prop on the component rather than as a field in the BvTableField interface.

Steps to reproduce the bug

1. Add a sortKey option to a field definition
2. Compile
3. 174:56 Type '{ key: string; sortable: true; label: string; sortKey: string; }' is not assignable to type 'string | ({ key: string; } & BvTableField)'.
   Object literal may only specify known properties, and 'sortKey' does not exist in type '{ key: string; } & BvTableField'.

Expected behavior

No compile error

Versions

Libraries:

• BootstrapVue: 2.21.2
• Bootstrap: 4.5.3
• Vue: 2.6.12

Environment:

• Device: Intel server
• OS: Ubuntu 18.04
• Browser: NA
• Version: NA