feat: recursive config search (#2166)

* refactor: experiments flags

* refactor: args.Parse

* feat: recursive search for taskrc files

* feat: consolidate some code into new fsext package

* feat: add tests for search and default dir

* fix: linting issues

taskrc/taskrc.go

@@ -0,0 +1,6 @@
+package taskrc
+
+var defaultTaskRCs = []string{
+	".taskrc.yml",
+	".taskrc.yaml",
+}