add adding courses guide

[kcmccormibm]

fixes #4941

@kaelynj let me know if this is okay! I added a new file and linked it in the README

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[kaelynj]

This looks great thank you @kcmccormibm! 🚀

[abbycross]

Suggested change

	1. Make a new folder for the course under `/learning/courses`. The name of this folder will be the slug of the course on the website. For example, `/learning/courses/my-course` will have the URL https://quantum.cloud.ibm.com/learning/my-course.
	1. Make a new folder for the course under `/learning/courses`. The name of this folder will be the slug of the course on the website. For example, `/learning/courses/my-course` will have the URL https://quantum.cloud.ibm.com/learning/courses/my-course.

[abbycross]

Suggested change

	3. Name each notebook so the filename matches the slug that page should have on the website. For example, `/learning/courses/my-course/my-file.ipynb` will have the URL https://quantum.cloud.ibm.com/learning/my-course/my-file.
	3. Name each notebook so the filename matches the slug that page should have on the website. For example, `/learning/courses/my-course/my-file.ipynb` will have the URL https://quantum.cloud.ibm.com/learning/courses/my-course/my-file.

[abbycross]

Suggested change

	4. Add the `title` and `description` to the first markdown cell of each notebook using frontmatter format, followed by a top-level heading:
	4. Add the `title` and `description` to the first markdown cell of each notebook using frontmatter format, followed by a top-level heading (see more info about formatting metadata [here](https://github.com/Qiskit/documentation/blob/main/mdx-guide.md#page-metadata), including min/max number of characters, and what types of characters will break the metadata (e.g., no colons)):

[abbycross]

Suggested change

	- If the images are not `.avif` or `.svg`, you must convert them to `.avif`. Use [ImageMagick](https://imagemagick.org/index.php) for this. You should be able to run `magick path/to/file.png path/to/file.avif` then delete the original file.
	- If the images are not `.avif` or `.svg`, you must convert them to `.avif` or `.svg`. Use [ImageMagick](https://imagemagick.org/index.php) for this. You should be able to run `magick path/to/file.png path/to/file.svg` then delete the original file.

I think svg is actually preferred, though I would need to confirm

[abbycross]

Suggested change

	- If the images are attachments in the notebook, you'll need to extract them to separate files. Speak to @Frank if you have any questions.
	- If the images are attachments in the notebook, you'll need to extract them to separate files. Speak to @kaelynj if you have any questions.

[abbycross]

Suggested change

	- With the image files in the correct place, update the markdown to point to the new images, leaving off the `public` part of the path. For example, if your file lives in `public/learning/images/courses/my-course/image.avif`, then your markdown should be:
	```markdown
	
	- With the image files in the correct place, update the markdown to point to the new images, leaving off the `public` part of the path. For example, if your file lives in `public/docs/learning/images/courses/my-course/image.avif`, then your markdown should be:
	```markdown
	

[abbycross]

Suggested change

16. With all the checks complete, start up the local preview by opening Rancher Desktop, then running `./start` in your terminal. Find your course and visit each page, checking carefully that everything is displaying correctly. If any pages crash (500 error), it's usually due to HTML in the notebook. If you can't work out why a page is crashing, speak to @Frank and he'll help you debug it.

16. With all the checks complete, start up the local preview by opening Rancher Desktop, then running `./start` in your terminal. Find your course and visit each page, checking carefully that everything is displaying correctly. If any pages crash (500 error), it's usually due to HTML in the notebook. If you can't work out why a page is crashing, speak to someone on the content team to help you debug it.

[abbycross]

Thanks so much Katie! I made a few clarifications and fixes.