Add optional Serene Seasons Age policies and seasonal pages (#38)

README.md

@@ -32,6 +32,12 @@ Biome pages, with cave and Nether biomes in a separate Cave Biome creative tab.
 TerraBlender Overworld/Nether regions extend compatible Age
 biome pools. See [the compatibility matrix](docs/TERRABLENDER_COMPATIBILITY.md)
 for supported versions and in-game verification.
+Serene Seasons 1.21.1 can maintain separate season progress in an Age dimension.
+Rivencraft automatically whitelists loaded Ages without a restart when Serene is installed;
+season pages can instead opt an Age out or hold it in one season.
+See [the optional compatibility guide](docs/SERENE_SEASONS_COMPATIBILITY.md)
+for the supported manual configuration and current limits; Rivencraft does not
+require Serene Seasons or GlitchCore.
 The Writing Desk can copy a selected written page from its collection tabs.
 The Writing Desk is now craftable from planks, a glass bottle, and a feather.
 It occupies two adjacent blocks, with one shared inventory; loaded paper and