feat(rustic): add 3rd party fallback completion loader

https://github.com/rustic-rs/rustic

Author: scop

completions/.gitignore

@@ -358,6 +358,7 @@
 /rpm2txz
 /rpmbuild
 /rpmbuild-md5
+/_rustic
 /s390-koji
 /sbcl-mt
 /scp

completions/Makefile.am

@@ -964,6 +964,7 @@ CLEANFILES = \
 	rpm2txz \
 	rpmbuild \
 	rpmbuild-md5 \
+	_rustic \
 	s390-koji \
 	sbcl-mt \
 	scp \
@@ -1326,7 +1327,11 @@ symlinks: $(DATA)
 	$(ss) mcrypt \
 		mdecrypt
 	$(ss) _mdbook \
-		_deno _diesel _dprint _starship
+		_deno \
+		_diesel \
+		_dprint \
+		_rustic \
+		_starship
 	$(ss) mfiutil \
 		mrsasutil
 	$(ss) mplayer \