docs(framework) Improve URLs orientation for better user experience

[KarhouTam]

Issue

Description

When users click on URLs in the READMEs that link to files or directories within the flower project, a webpage will open displaying the content found in their local flower project directory.

So maybe a better URL should link to the file/directory at the local rather than on https://github.com/adap/flower/tree/main/.

Proposal

Explanation

Change all URLs in READMEs that have the prefix https://github.com/adap/flower/tree/main/ or https://github.com/adap/flower/blob/main/ to relative paths, e.g.,

A URL in flower/examples/advanced-pytorch/README.md:
https://github.com/adap/flower/tree/main/examples/quickstart-pytorch -> ../quickstart-pytorch/README.md

Besides, I added README.md at the end of some URLs for better orientation.

Modified URLs will function the same as before when clicked on the website, and will be more logical locally.

Demonstration

before.mp4

after.mp4

[KarhouTam]

"The code in this directory is fairly similar to that presented in [simulation-pytorch example] (../simulation-pytorch)"

Btw, seems simulation-pytorch is deprecated.

[jafermarq]

Thank @KarhouTam ! @tanertopal what do you think about these changes to the URL?

[KarhouTam]

Hi, @tanertopal . What do you think about these changes? I think they are not harmful at all and make flower developers maintein the URLs easier.