Can't use dash in filename when using "New Tab" feature in 1.8.5-1.8.9-1.9beta

### Context
Tested on Arduino IDE 1.8.5, 1.8.9 and 1.9beta on Ubuntu.

### Steps to reproduce
1. In any project, click on the triangle/down-arrow in the top right of the IDE.
2. Select the option "New Tab"
3. An input field appears asking for a file name. Enter "somename-with-a-dash"

### Expected behavior
4. The file name appears in the input field.

### Actual behavior
4. The input doesn't respond to the "-" symbol when entering filenames (underscore works as expected)

Reproduce the issue in the Arduino IDE's New Tab filename input on Ubuntu, then trace the input handling for filename characters. Done means filenames containing a dash are accepted, while the existing underscore behavior continues to work.

Written by the indexing model from the issue text.