Add cosmic-reader

recipes/tools/cosmic-reader/manifest

+name=COSMIC Reader
+binary=/bin/cosmic-reader
+icon=/ui/icons/apps/accessories-text-editor.png
+accept=*.pdf
+author=Jeremy Soller
+description=COSMIC Reader

recipes/tools/cosmic-reader/recipe.toml

+[source]
+git = "https://github.com/pop-os/cosmic-reader.git"
+branch = "master"
+
+[build]
+template = "custom"
+script = """
+cookbook_cargo --no-default-features
+mkdir -pv "${COOKBOOK_STAGE}/ui/apps"
+cp -v "${COOKBOOK_RECIPE}/manifest" "${COOKBOOK_STAGE}/ui/apps/40_cosmic-reader"
+"""