Fix selection and context menu type annotations

[aaronbeall]

Context

1. Type definitions incorrectly say getSelected() returns a Range which is an object from the DOM, but it should be CellRange which is the handsontable object described in the docs.
2. Type annotation for context menu hooks use object which should be ContextMenu plugin instance

How has this been tested?

Tested with npm run test:types

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature or improvement (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Additional language file or change to the existing one (translations)

Related issue(s):

Checklist:

• My code follows the code style of this project,
• My change requires a change to the documentation.

[AMBudnik]

Thank you for sharing the PR @aaronbeall

[pnowak]

👍

[AMBudnik]

Always happy to inform about the PR being published. Thank you @aaronbeall ~
It's available in v 6.2.0+