You could use the vi(1) editor, but a "pager" such as less(1) or more(1) could also be used without the risk of accidentally editing a file. The names of the README files in that directory are the package names, so you could use something like
$ less /usr/local/share/doc/pkg-readmes/openvpn or you could change to the directory and list the files within, then select a file to review with a pager utility. For example, on this laptop I'm using:
Code:
t450$ cd /usr/local/share/doc/pkg-readmes/
t450$ ls
avahi dbus gnupg jdk-11 qemu-ga texlive_base
chromium ffmpeg gtk+2 keepassxc rawtherapee tor-browser
consolekit2 firefox gtk+3 libgphoto sane-backends udfclient
cups foomatic-db-engine gtk+4 llvm sdl2 xdg-utils
cups-filters git hplip-common miniupnpc tarsnap-gui
cvechecker glib2 jack qemu terminus-font
t450$ less firefox