Use selected text for project search

[vkbo]

Summary:

This PR changes the begin search function for the project search panel to use selected text from the editor if the editor has focus when the search is activated.

Related Issue(s):

Closes #1789

Reviewer's Checklist:

• The header of all files contain a reference to the repository license
• The overall test coverage is increased or remains the same as before
• All tests are passing
• All flake8 checks are passing and the style guide is followed
• Documentation (as docstrings) is complete and understandable
• Only files that have been actively changed are committed