feat: Add Sigma File Manager (#2045)

apps/sigma-file-manager/sigma-file-manager.yml

@@ -0,0 +1,14 @@
+name: Sigma File Manager
+description: '"Sigma File Manager" is a free, open-source, quickly evolving, modern file manager (explorer / finder) app for Windows and Linux.'
+website: 'https://github.com/aleksey-hoffman/sigma-file-manager'
+repository: 'https://github.com/aleksey-hoffman/sigma-file-manager'
+category: 'Utilities'
+license: 'GNU GPLv3 or later'
+keywords:
+  - modern
+  - file
+  - manager
+  - explorer
+  - file-manager
+  - browser
+  - vue