(changelog): Write up initial changelog for 1.25.0
(changelog): Write up initial changelog for 1.25.0

Signed-off-by: Daniel Silverstone <3cc17a76d780e0cd3d87bad586a1c53967be5625@digital-scurf.org>

rust-lang/rustup,rust-lang/rustup,rust-lang/rustup,rust-lang/rustup,rust-lang/rustup