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-whitespace

@@ -0,0 +1,26 @@
+#!/bin/bash
+
+# Check for trailing whitespace at end of lines.
+
+# Exit on first failing command.
+set -e
+# Exit on unset variable.
+set -u
+
+FOUND_TRAILING_WHITESPACE=0
+
+while read -r line; do
+  if grep \
+    "\s$" \
+    --line-number \
+    --with-filename \
+    --binary-files=without-match \
+    --exclude="*.svg" \
+    --exclude="*.eps" \
+    "${line}"; then
+    echo "ERROR: Found trailing whitespace" >&2;
+    FOUND_TRAILING_WHITESPACE=1
+  fi
+done < <(git ls-files)
+
+exit "${FOUND_TRAILING_WHITESPACE}"