manual: link directly to gerrit for proposing changes

This is, well, interesting. It's the same "edit" button you see on
Gitiles, and upon clicking it, without confirmation, it makes a new CL
and dumps you directly into the editor for the file in question.

I guess if you click it by accident you can just abandon or delete the
CL so it's like, fine. A bit of fascinating UX design here.

Change-Id: I765a1f1fc6d94b171878dde7b01fc621adc00180

doc/manual/book.toml

@@ -7,9 +7,8 @@ create-missing = false
 [output.html]
 additional-css = ["custom.css"]
 additional-js = ["redirects.js"]
-# Using our GitHub mirror enables easier typo fixes since there is no easy way
-# to just submit a Gerrit CL by the web for trivial stuff.
-edit-url-template = "https://github.com/lix-project/lix/tree/main/doc/manual/{path}"
+# Jumps directly into a new Gerrit CL editing the file in question.
+edit-url-template = "https://gerrit.lix.systems/admin/repos/edit/repo/lix/branch/main/file/doc/manual/{path}"
 git-repository-url = "https://git.lix.systems/lix-project/lix"
 # Folding by default would prevent things like "Ctrl+F for nix-env" from working
 # trivially, but the user should be able to fold if they want to.