Merge pull request #4231 from Falseee/Falseee/du/fix/code-guidelines

updated the code guidelines (use semicolons => dont use semicolons)

CONTRIBUTING.md

@@ -200,9 +200,8 @@ includes code changes) and under the terms of the
 ## Code guidelines
 
 - Readability
-- Need semicolons
-- 4 spaces (no tabs)
-- strict mode
+- [no semicolons](https://github.com/wenzhixin/bootstrap-table/pull/4218#issuecomment-475822706)
+- 2 spaces (no tabs)
 - "Attractive"