fix(command line): markdown_root url

[sambacha]

• Fixes the path to correctly have tree in front of the {branch} for generating a correct URL.

• Fixes replacing tree/ with blob/HEAD so that the generated URL does not have to define the default branch name in the case that master is not the default branch name.

Note that to return blob/HEAD the supplied URL must contain tree/, this does not provide a detection in the case that the first URL is incorrect.

[0xalpharush]

Can you give an example for when this isn't working? It works like slither . --checklist --markdown-root https://github.com/ORG/REPO/blob/COMMIT/ normally

[sambacha]

Can you give an example for when this isn't working? It works like slither . --checklist --markdown-root https://github.com/ORG/REPO/blob/COMMIT/ normally

When just using the remote origin URL, i.e. https://github.com/ORG/REPO/

I understand for GitHub Workflow CI this works:

        slither-args: --checklist --markdown-root ${{ github.server_url }}/${{ github.repository }}/blob/${{ github.sha }}/