Directly link changelog from quick-links section in 'README.md' file

Author: regexident

README.md

@@ -42,6 +42,7 @@ https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Frls-2.2E0
 * Website: https://rust-analyzer.github.io/
 * Metrics: https://rust-analyzer.github.io/metrics/
 * API docs: https://rust-analyzer.github.io/rust-analyzer/ide/
+* Changelog: https://rust-analyzer.github.io/thisweek
 
 ## License