Move internal modules to “internal” folder.

.internal/escapeStringChar.js

@@ -0,0 +1,22 @@
+/** Used to escape characters for inclusion in compiled string literals. */
+const stringEscapes = {
+  '\\': '\\',
+  "'": "'",
+  '\n': 'n',
+  '\r': 'r',
+  '\u2028': 'u2028',
+  '\u2029': 'u2029'
+};
+
+/**
+ * Used by `template` to escape characters for inclusion in compiled string literals.
+ *
+ * @private
+ * @param {string} chr The matched character to escape.
+ * @returns {string} Returns the escaped character.
+ */
+function escapeStringChar(chr) {
+  return `\\${ stringEscapes[chr] }`;
+}
+
+export default escapeStringChar;