Provide an example .golangci.yml file

The default [.golangci.yml](https://github.com/golangci/golangci-lint/blob/master/.golangci.example.yml) file is great, but fairly large to grok. To show how to enable the linter specifically, we here provide a trimmed down example of the file that enables JUST the example linter (and typecheck).

Author: dbraley

.golangci.yml

@@ -0,0 +1,15 @@
+linters-settings:
+  custom:
+    example:
+#      Path is required
+      path: example.so
+#      description is optional
+      description: The description of the linter. This is optional, but shows up when running `golangci-lint linters`.
+#      original-url is optional, and is only used for documentation purposes.
+      original-url: github.com/golangci/example-linter
+linters:
+  disable-all: true
+  enable:
+    - example
+#    Typecheck is how golangci-lint reports compile errors, so should always be enabled.
+    - typecheck