feat: truncate content exceeding the byte limit (#129)

__test__/readme-helper.unit.test.ts

@@ -1,4 +1,4 @@
-import {completeRelativeUrls} from '../src/readme-helper'
+import {completeRelativeUrls, truncateToBytes} from '../src/readme-helper'
 
 describe('complete relative urls tests', () => {
   const GITHUB_SERVER_URL = process.env['GITHUB_SERVER_URL']
@@ -333,3 +333,12 @@ describe('complete relative urls tests', () => {
     )
   })
 })
+
+describe('truncate to bytes tests', () => {
+  test('unicode aware truncation to a number of bytes', async () => {
+    expect(truncateToBytes('test string to be truncated', 10)).toEqual(
+      'test strin'
+    )
+    expect(truncateToBytes('😀😁😂🤣😃😄😅', 10)).toEqual('😀😁')
+  })
+})