[fractal] git: Ignore Flatpak workfiles

[Daniel Garcia Moreno <danigm src gnome org>]

commit fce71313d342959a487560905aa0f4bbd109ff19
Author: Juraj Fiala <jurf riseup net>
Date:   Thu Jun 25 17:11:05 2020 +0200

    git: Ignore Flatpak workfiles
    
    When manually building Fractal with Flatpak, it creates these folders:
    
    - .flatpak-builder/ -- cache folder for downloads/builds
    - fractal/ -- build folder, name recommended by the README
    
    Also add .flatpak files (Flatpak bundles), useful when creating builds you want to share for testing.

 .gitignore | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/.gitignore b/.gitignore
index 38ade21f..a27d58dd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,8 @@ vendor
 # Files configured by meson
 fractal-gtk/src/config.rs
 fractal-gtk/src/static_resources.rs
+
+# Files created by Flatpak
+.flatpak-builder/
+fractal/
+*.flatpak