Add dart support (#919)

Co-authored-by: Alex Goodman <alex.goodman@anchore.com>

test/integration/test-fixtures/image-pkg-coverage/pkgs/dart/pubspec.lock

@@ -0,0 +1,49 @@
+# Generated by pub
+# See https://dart.dev/tools/pub/glossary#lockfile
+packages:
+  ale:
+    dependency: transitive
+    description:
+      name: ale
+      url: "https://pub.hosted.org"
+    source: hosted
+    version: "3.3.0"
+  analyzer:
+    dependency: transitive
+    description:
+      name: analyzer
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.40.7"
+  ansicolor:
+    dependency: transitive
+    description:
+      name: ansicolor
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.1"
+  archive:
+    dependency: transitive
+    description:
+      name: archive
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.13"
+  args:
+    dependency: transitive
+    description:
+      name: args
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.6.0"
+  key_binder:
+    dependency: "direct main"
+    description:
+      path: "."
+      ref: HEAD
+      resolved-ref: "3f7b3a6350e73c7dcac45301c0e18fbd42af02f7"
+      url: "git@github.com:Workiva/key_binder.git"
+    source: git
+    version: "1.11.20"
+sdks:
+  dart: ">=2.12.0 <3.0.0"