Add FileSelection dialog type

This patch adds the FileSelection struct representing a file selection
dialog.  It can be displayed using the backend’s show_file_selection
function.

Currently, we only support file open dialogs (i. e.  choosing an
existing file).  Support for save dialogs should be added in the future.

1 files changed, 1 insertions, 0 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 57bc68f..355b789 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,3 +16,4 @@ license = "MIT"
 
 [dependencies]
 rpassword = "2"
+dirs = "2.0"