update the tasks for linter, spell checker and codes check

Author: SarahAlidoost

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,21 +2,23 @@
 
 Thanks for contributing!
 Please keep in mind that lesson maintainers are volunteers and it may be some time before they can respond to your contribution. Although not all contributions can be incorporated into the lesson materials, we appreciate your time and effort to improve the curriculum.
+
 * * *
 
 ## Tasks
 
 - [ ] Read [CONTRIBUTING.md](https://github.com/ESMValGroup/tutorial/blob/master/CONTRIBUTING.md).
 - [ ] Create an [issue](https://github.com/ESMValGroup/tutorial/issues) to discuss what you are going to do.
 - [ ] Give this pull request a descriptive title.
-- [ ] If you are contributing to the lesson materials, make sure the content does not have spelling or grammar errors.
-- [ ] Please use `markdownlint` to check that your files do not contain errors.
-- [ ] Preview changes on your own machine before pushing them to GitHub by running `make docker-serve`.
+- [ ] If you are contributing to the lesson materials, make sure the content does not have spelling or grammar errors. See `Lesson development` in [CONTRIBUTING.md](https://github.com/ESMValGroup/tutorial/blob/master/CONTRIBUTING.md).
+- [ ] Please use a `markdown lint tool` to check that your files do not contain errors. See `Lesson development` in[CONTRIBUTING.md](https://github.com/ESMValGroup/tutorial/blob/master/CONTRIBUTING.md).
+- [ ] Preview changes on your own machine before pushing them to GitHub by running `make serve`, alternatively `make docker-serve`. See `Lesson development` in[CONTRIBUTING.md](https://github.com/ESMValGroup/tutorial/blob/master/CONTRIBUTING.md).
+- [ ] All code instructions have been tested.
 
 ## More tasks for a new episode
 
-- [ ] Follow `Lesson Organization` in [CONTRIBUTING.md](https://github.com/ESMValGroup/tutorial/blob/master/CONTRIBUTING.md).
-- [ ] Follow `Lesson Formatting` in [CONTRIBUTING.md](https://github.com/ESMValGroup/tutorial/blob/master/CONTRIBUTING.md).
+- [ ] Follow `Lesson organization` in [CONTRIBUTING.md](https://github.com/ESMValGroup/tutorial/blob/master/CONTRIBUTING.md).
+- [ ] Follow `Lesson formatting` in [CONTRIBUTING.md](https://github.com/ESMValGroup/tutorial/blob/master/CONTRIBUTING.md).
 
 If you need help with any of the tasks above, please do not hesitate to ask by commenting in the issue or pull request.