Update free-courses-es.md

[SrishBansal]

Added a new introduction to python course

What does this PR do?

Add resource(s)

For resources

Description

Added a new easy to understand introduction to python course.

Why is this valuable (or not)?

How do we know it's really free?

For book lists, is it a book? For course lists, is it a course? etc.

Checklist:

• Read our contributing guidelines.
• Search for duplicates.
• Include author(s) and platform where appropriate.
• Put lists in alphabetical order, correct spacing.
• Add needed indications (PDF, access notes, under construction).
• Used an informative name for this pull request.

Follow-up

• Check the status of GitHub Actions and resolve any reported warnings!

[github-actions]

Linter failed, fix the error(s):

free-programming-books/courses/free-courses-es.md
305:1-306:159  warning  Incorrect number of blank lines between last section and next heading  blank-lines-1-0-2  remark-lint
 308:1-308:11  warning  Incorrect number of blank lines between heading and section            blank-lines-1-0-2  remark-lint

[github-actions]

Linter failed, fix the error(s):

free-programming-books/courses/free-courses-es.md
206:1-225:162  warning  Incorrect number of blank lines between last section and next heading  blank-lines-1-0-2  remark-lint
 227:1-227:11  warning  Incorrect number of blank lines between heading and section            blank-lines-1-0-2  remark-lint
228:1-228:116  warning  Incorrect number of blank lines between last section and next heading  blank-lines-1-0-2  remark-lint