Add show-all flag to glossary() and test-case

glossy/tests/show-all/test.typ

@@ -0,0 +1,33 @@
+#import "/lib.typ": *
+
+#show: init-glossary.with((
+  one: "this is term one",
+  two: "term two also"
+))
+
+#set page(
+  margin: 1em,
+  width: 3.5in,
+  height: auto,
+)
+#set text(size: 10pt)
+
+In this document we don't reference our glossary items but expect them to be
+shown anyway.
+
+#glossary(show-all: true)
+
+#glossary(
+  theme: theme-chicago-index,
+  show-all: true
+)
+
+#glossary(
+  theme: theme-compact,
+  show-all: true
+)
+
+#glossary(
+  theme: theme-table,
+  show-all: true
+)