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

https://github.com/ibotta/sopstool#usage

Author: scop

completions/.gitignore

@@ -365,6 +365,7 @@
 /smbpasswd
 /smbtar
 /smbtree
+/_sopstool
 /sparc-koji
 /spovray
 /_sshi

completions/Makefile.am

@@ -971,6 +971,7 @@ CLEANFILES = \
 	smbpasswd \
 	smbtar \
 	smbtree \
+	_sopstool \
 	sparc-koji \
 	spovray \
 	_sshi \
@@ -1097,7 +1098,11 @@ symlinks: $(DATA)
 	$(ss) freeciv-server \
 		civserver
 	$(ss) _gaiacli \
-		_gaiad _ngrok _npm _tendermint
+		_gaiad \
+		_ngrok \
+		_npm \
+		_sopstool \
+		_tendermint
 	$(ss) gcc \
 		c++ cc f77 f95 g++ g++-5 g++-6 g++-7 g++-8 g77 g95 gcc-5 \
 		gcc-6 gcc-7 gcc-8 gccgo gccgo-5 gccgo-6 gccgo-7 gccgo-8 gcj \