Ipyfilechooser

New features:
- The ability to restrict file browsing to a `sandbox_path` folder has finally been added! (Fixes 35)
- Filenames can not contain path separator characters or parent folder strings (i.e., '..')
- `use_dir_icons` has been replaced with `dir_icon` which allows for customizing the folder icon (Fixes 22)
- `dir_icon_append` can now be used to put the folder icon before or after the folder name
- Better error handling with `ParentPathError`, `InvalidPathError`, and `InvalidFileNameError`

Bug fixes:
- Better and more consistent handling of Windows drive letters and paths
- Fix bug where resetting the filechooser would not reenable the select/change button
- Properly handle folder permission errors by raising a warning

Updates and fixes:
- Widget width is now configurable using the `layout` property and a `Layout` object (fixes 56)
- Folder paths are now normalized using `os.path.normpath` which properly handles '/' and '\\' on Windows (fixes 59)
- The widget now supports the `value` property to align with other widget types (fixes 57)
- The label showing the selected value now reflows the text to new lines as required (and shows a scrollbar if the value is too long)
- Buttons now have a minimum width so their text is always visible, regardless of widget width

A big thank you to tombelpasso for identifying and submitting the above issues.

Updates:
- Added typing hints (Mandroide)
- Updated max line length check from 90 to 120 characters
- Fixed `filter_pattern` values not being treated as case-insensitive (fixes https://github.com/crahan/ipyfilechooser/issues/49)
- General code cleanup

Updates:
- Prevent applying the selected value if the filename doesn't match one of the `filter_pattern` values (fixes https://github.com/crahan/ipyfilechooser/issues/38)

Updates:
- Added ability to specify a list of `fnmatch` pattern strings for `filter_pattern` https://github.com/crahan/ipyfilechooser/issues/34

Updates:
- Fixed issue with `select_default` not being applied on `reset` https://github.com/crahan/ipyfilechooser/issues/32