Simply Legacy 1.2.6

Updated to Legacy Modpack Resources 5.1.0

Mainly to fix a bunch of issues caused by overwritten changes during development, notably also adding some more How to Play refinements

Added changelog on first launch

When launching the modpack for the first time, the changelog screen will now be displayed. This should also show up once we release a version with Minecraft 26.1, though not for 1.21.11.