feat: compare doc and indicate in icon (#8)

* feat: compare doc and indicate in icon

- refactoring
- perform quick compare between doc of A and B
- indicate difference in icon
- show it with green icon if A and B doc is same
- show it with yellow icon if A and B doc is different

* fix: remove stored generated yaml doc for memory

- remove doc that stores generated yaml string to reduce memory usage
- introduce compare func instead of direct comparison from stored string of yaml

* fix: add KubeMani Diff prefix for context menu title

Author: sunggun-yu

package.json

@@ -121,7 +121,7 @@
       },
       {
         "command": "kubemani-diff.selectFiles",
-        "title": "Select Kubernetes Manifest files to compare",
+        "title": "KubeMani Diff: Select Kubernetes Manifest files to compare",
         "category": "KubeMani Diff"
       },
       {