Additional Information Added to README.md

[alisianguyen]

Updating the README.md with adding basic installation steps for macOS and Windows, general troubleshooting, and adding an accessible hyperlink for licensing information.

Developer Certificate of Origin
Version 1.1

Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
1 Letterman Drive
Suite D4700
San Francisco, CA, 94129

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.

Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
have the right to submit it under the open source license
indicated in the file; or

(b) The contribution is based upon previous work that, to the best
of my knowledge, is covered under an appropriate open source
license and I have the right under that license to submit that
work with modifications, whether created in whole or in part
by me, under the same open source license (unless I am
permitted to submit under a different license), as indicated
in the file; or

(c) The contribution was provided directly to me by some other
person who certified (a), (b) or (c) and I have not modified
it.

(d) I understand and agree that this project and the contribution
are public and that a record of the contribution (including all
personal information I submit with it, including my sign-off) is
maintained indefinitely and may be redistributed consistent with
this project or the open source license(s) involved.

[welcome]

Thanks for opening this pull request! Please check out our contributing guidelines and check for the automated tests.

[ghutchis]

I appreciate the build comments, but I think it's probably better suited to go into https://github.com/Avogadro/two.avogadro.cc/blob/main/source/install/build.md for https://two.avogadro.cc/

Also you don't need homebrew on Mac to build Avogadro. Qt has Mac builds available, and it's also possible to just use aqtinstall https://aqtinstall.readthedocs.io/en/latest/installation.html