Bump version and adjust changelog #908

Job	Run time
Test (nightly)	2m 55s
MSRV	37s
Test (macOS)	1m 19s
Build docs	25s
Examples	3m 3s
Check minimal versions	32s
Test (stable)	3m 19s
Test (beta)	2m 56s
Test (Windows)	6m 9s
Test (native-tls)	2m 42s
Test (no default features)	48s
Test (no cache)	2m 52s
Test (no gateway)	1m 36s
Test (unstable Discord API features)	3m 5s
Test (simd-json)	3m 9s
Test (chrono, chrono)	36s
Test (unstable API + typesize, default unstable_discord_api typesize, true)	52s
Test (builder without model, builder, true)	1m 2s
Test (unstable Discord API (no default features), unstable_discord_api, true)	17s
	38m 14s

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