Rename doc/manual{src -> source}

This is needed to avoid this
https://github.com/mesonbuild/meson/issues/13774 when we go back to
making our subproject directory `src`.

doc/manual/source/release-notes/rl-2.22.md

@@ -0,0 +1,21 @@
+# Release 2.22.0 (2024-04-23)
+
+### Significant changes
+
+- Remove experimental repl-flake [#10103](https://github.com/NixOS/nix/issues/10103) [#10299](https://github.com/NixOS/nix/pull/10299)
+
+  The `repl-flake` experimental feature has been removed. The `nix repl` command now works like the rest of the new CLI in that `nix repl {path}` now tries to load a flake at `{path}` (or fails if the `flakes` experimental feature isn't enabled).
+
+### Other changes
+
+- `nix eval` prints derivations as `.drv` paths [#10200](https://github.com/NixOS/nix/pull/10200)
+
+  `nix eval` will now print derivations as their `.drv` paths, rather than as
+  attribute sets. This makes commands like `nix eval nixpkgs#bash` terminate
+  instead of infinitely looping into recursive self-referential attributes:
+
+  ```ShellSession
+  $ nix eval nixpkgs#bash
+  «derivation /nix/store/m32cbgbd598f4w299g0hwyv7gbw6rqcg-bash-5.2p26.drv»
+  ```
+