test(glossy): add bin/autotest.sh (uses watchexec)

glossy/bin/autotest.sh

@@ -0,0 +1,6 @@
+watchexec \
+  --watch . \
+  --clear \
+  --ignore 'tests/**/diff/**' \
+  --ignore 'tests/**/out/**' \
+  "typst-test r"