Bump chezmoi.io/themes/book from a486adf to e53a638

Bumps [chezmoi.io/themes/book](https://github.com/alex-shpak/hugo-book) from `a486adf` to `e53a638`.
- [Release notes](https://github.com/alex-shpak/hugo-book/releases)
- [Commits](alex-shpak/hugo-book@a486adf...e53a638)

Signed-off-by: dependabot[bot] <[email protected]>