A non command line solution that worked for me was to search for the package on debian`s repo website. Once you find the package version you are interested in, you click on it and you are navigated to the package details.
On the right hand side menu there is a heading "Download Source Package" followed by the package name. In my case:
Download Source Package libxml2:
Once you click on that link you are navigated to another page which lists the binary files included in the package with some other information. Again on the right hand side menu under the heading Debian Resources there is a link named "Debian Changelog" which contains the changes of the package.