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/language_test.go

@@ -66,6 +66,10 @@ func TestLanguageFromPURL(t *testing.T) {
 			purl: "pkg:hex/hpax/hpax@0.1.1",
 			want: UnknownLanguage,
 		},
+		{
+			purl: "pkg:cran/base@4.3.0",
+			want: R,
+		},
 	}
 
 	var languages []string
@@ -231,6 +235,10 @@ func TestLanguageByName(t *testing.T) {
 			name:     "haskell",
 			language: Haskell,
 		},
+		{
+			name:     "R",
+			language: R,
+		},
 	}
 
 	for _, test := range tests {