v2.6.0

• Please refer to https://fzyzcjy.github.io/flutter_rust_bridge/guides/miscellaneous/whats-new for what's changed in V2.
• Update syn as a transitive dependency to version 2.0 #2371 (thanks @anlumo)
• Auto detect and use fvm #2390
• More full support of raw identifiers #2391
• Clear up symbols #2392
• Allow ui_state attribute to be used with arbitrary associated struct name #2393