Add golangci-lint config excluding errcheck noise

Exclude fmt.Fprint* (best-effort status output) and io.Closer.Close
(deferred cleanup) from errcheck — covers all 13 findings from the
linter's first real run.

Author: luthermonson

.golangci.yml

@@ -0,0 +1,10 @@
+version: "2"
+
+linters:
+  settings:
+    errcheck:
+      exclude-functions:
+        - fmt.Fprint
+        - fmt.Fprintf
+        - fmt.Fprintln
+        - (io.Closer).Close