add tfplan.binary and tfplan.json to git ignore file, so the plan file used by conftest won't be committed

Author: lonegunmanb

terraform/git_ignore.grept.hcl

@@ -21,6 +21,8 @@ locals {
     "terraform.rc",
     ".DS_Store",
     "*.md.tmp",
+    "**/tfplan.binary",
+    "**/tfplan.json",
   ])
 }