fix(git): add alias and tag signing

- sign tags by default
- add `graph` alias

Signed-off-by: Matej Focko <me@mfocko.xyz>

playbooks/roles/git/templates/gitconfig.j2

@@ -1,5 +1,6 @@
 [alias]
 	scommit = commit --signoff
+	graph = log --oneline --decorate --graph --all
 
 [commit]
 	gpgsign = true
@@ -26,6 +27,9 @@
 [rebase]
 	autoStash = true
 
+[tag]
+	gpgSign = true
+
 [user]
 	name       = Matej Focko
 	email      = {{ git_email }}