Normalize whitespace in source files

Ensure that no source files have trailing whitespace at end of lines and ensure that all files end with a single trailing newline.

This also adds Github Actions to enforce whitespace conventions.

.github/workflow-scripts/check-trailing-newline

@@ -0,0 +1,37 @@
+#!/bin/bash
+
+# Verify that all text files end in a trailing newline.
+
+# Exit on first failing command.
+set -e
+
+# Exit on unset variable.
+set -u
+
+success=0
+
+function is_plaintext_file() {
+  local file="$1"
+  if [[ $file == *.svg ]]; then
+    echo ""
+    return
+  fi
+  file --brief "${file}" | grep text
+}
+
+# Split strings on newlines.
+IFS='
+'
+for file in $(git ls-files)
+do
+  if [[ -z $(is_plaintext_file "${file}") ]]; then
+    continue
+  fi
+
+  if ! [[ -z "$(tail -c 1 "${file}")" ]]; then
+    printf "File must end in a trailing newline: %s\n" "${file}" >&2
+    success=255
+  fi
+done
+
+exit "${success}"