Course Overview (skills#318)

* Update README.md

step one updates

* Update README.md

* adding updated create-new-file pn

* Delete create-new-file.png

removing previous create-new-file image

* uploading new create-new-file png

* updated step 3

* final content updates

* Delete Pull-request-description.png

* Add files via upload

* Delete commit-full-screen.png

* adding updated commit-full-screen image

* Delete pull-request-branches.png

* added updated pull-request-branches image

* updated image callouts

* added profile readme example image

* added create-branch-button png

* added additional images

* Delete my-first-branch.png

* final clean up for PR

* Update README.md

Co-authored-by: Emily Gould <[email protected]>

* Update README.md

Co-authored-by: Emily Gould <[email protected]>

* moved "Course tips" into the welcome section

* updated What is GitHub video link

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Co-authored-by: Emily Gould <[email protected]>

Author: cmwilson21