Added Course on Linked Lists

[metabiswadeep]

What does this PR do?

Added a course on linked lists.

Description

Absolutely Free course to learn linked lists

Checklist:

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

Follow-up

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

[metabiswadeep]

Please tell if any other changes are necessary before merging this PR @eshellman

[metabiswadeep]

Done @eshellman

[eshellman]

please resolve conflicts.