Fix external manifest for extension fallback documented but not yet implemented

Update for rc1

Author: luc-github

dist/BUNDLE_SIZES.md

@@ -4,13 +4,13 @@ Generated by `tools/release_bundle_sizes.py`. Use this table in RELEASE_*.md or
 
 | Target | Subtarget | Gzip Path | Gzip Size | Brotli Path | Brotli Size |
 |--------|-----------|-----------|-----------|-------------|-------------|
-| CNC | GRBL | CNC\GRBL\index.html.gz | 92.0 KB | CNC\GRBL\index.html.br | 76.3 KB |
-| CNC | GRBLHal | CNC\GRBLHal\index.html.gz | 96.7 KB | CNC\GRBLHal\index.html.br | 79.6 KB |
-| Printer3D | Marlin | Printer3D\Marlin\index.html.gz | 98.0 KB | Printer3D\Marlin\index.html.br | 80.8 KB |
-| Printer3D | Marlin-embedded | Printer3D\Marlin-embedded\index.html.gz | 97.4 KB | Printer3D\Marlin-embedded\index.html.br | 80.5 KB |
-| Printer3D | Repetier | Printer3D\Repetier\index.html.gz | 96.8 KB | Printer3D\Repetier\index.html.br | 80.0 KB |
-| Printer3D | Smoothieware | Printer3D\Smoothieware\index.html.gz | 96.4 KB | Printer3D\Smoothieware\index.html.br | 79.5 KB |
-| SandTable | GRBL | SandTable\GRBL\index.html.gz | 84.2 KB | SandTable\GRBL\index.html.br | 69.7 KB |
+| CNC | GRBL | CNC\GRBL\index.html.gz | 92.1 KB | CNC\GRBL\index.html.br | 76.4 KB |
+| CNC | GRBLHal | CNC\GRBLHal\index.html.gz | 96.9 KB | CNC\GRBLHal\index.html.br | 79.8 KB |
+| Printer3D | Marlin | Printer3D\Marlin\index.html.gz | 98.2 KB | Printer3D\Marlin\index.html.br | 81.0 KB |
+| Printer3D | Marlin-embedded | Printer3D\Marlin-embedded\index.html.gz | 97.6 KB | Printer3D\Marlin-embedded\index.html.br | 80.6 KB |
+| Printer3D | Repetier | Printer3D\Repetier\index.html.gz | 96.9 KB | Printer3D\Repetier\index.html.br | 80.0 KB |
+| Printer3D | Smoothieware | Printer3D\Smoothieware\index.html.gz | 96.6 KB | Printer3D\Smoothieware\index.html.br | 79.7 KB |
+| SandTable | GRBL | SandTable\GRBL\index.html.gz | 84.4 KB | SandTable\GRBL\index.html.br | 69.8 KB |
 
-**Total Gzip size:** 661.6 KB (677445 bytes).
-**Total Brotli size:** 546.4 KB (559505 bytes).
+**Total Gzip size:** 662.7 KB (678638 bytes).
+**Total Brotli size:** 547.3 KB (560456 bytes).