Add favicon and logo generation scripts

- Implemented `generate-favicons.js` to create various favicon formats from a single SVG file.
- Created `update-data.js` to scan logo directories, generate PNG and JPG images from SVGs, and update the logos JSON data.
- Added a `.gitignore` file in the `flags_gen` directory to exclude all files except the `.gitignore` itself.
- Updated `logos.json` to ensure proper formatting.

public/data/logos.json

@@ -3589,4 +3589,4 @@
     ],
     "brand": "Bvr"
   }
-]
+]

public/flags_gen/.gitignore

@@ -0,0 +1,2 @@
+*
+!.gitignore