feat: Add R cataloger (#1790)

Add a cataloger that detects installed R packages by looking for DESCRIPTION
files. The base R package is now picked up in coverageImage tests in
test/cli/packages_cmd_test.go, so increment expected package counts for the
tests that use that image.

Signed-off-by: Will Murphy <will.murphy@anchore.com>

syft/pkg/cataloger/r/package_test.go

@@ -0,0 +1,14 @@
+package r
+
+import "testing"
+
+func Test_newPackage(t *testing.T) {
+	testCases := []struct {
+		name string
+	}{}
+
+	for _, tt := range testCases {
+		t.Run(tt.name, func(t *testing.T) {
+		})
+	}
+}