Update install instructions

[alanocallaghan]

No description provided.

[Rylern]

I tried the pip install commands but they didn't work, is it because the repo is private?

[alanocallaghan]

The first one (pip install --upgrade https://github.com/qupath/qubalab/tarball/main) fails for me with a 404, which yeah must be a visibility issue

The second one (pip install git+https://github.com/qupath/qubalab.git) actually runs fine for me. I get:

Defaulting to user installation because normal site-packages is not writeable
Collecting git+https://github.com/qupath/qubalab.git
  Cloning https://github.com/qupath/qubalab.git to /tmp/pip-req-build-dlecw9de
  Running command git clone --filter=blob:none --quiet https://github.com/qupath/qubalab.git /tmp/pip-req-build-dlecw9de
  Resolved https://github.com/qupath/qubalab.git to commit fad10bf946f5e1e1ff4df1d9085d48f517e04849

...but this is because I have this in my ~/.gitconfig:

[url "ssh://[email protected]/"]
    insteadOf = https://github.com/

so yes probably also visibility