Add script/lint-fix entrypoint and make lint-fix shim (refs #61)

script/lint-fix

@@ -0,0 +1,15 @@
+#!/bin/sh
+# script/lint-fix: run the linter's autofixer. Rewrites files in place
+# for every finding the enabled linters know how to fix; findings
+# without an autofix are reported but left alone (exit status is
+# nonzero while any remain).
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    golangci-lint run --fix ./...
+}
+
+main "$@"