Below is my example of a well structured Readme file for a code base maintained in an organisation. The ordering isn't that important but the information is. Linking out to other things can be ok although in my experience I believe things directly related to the code should live next to the code, including documentation.
A short paragraph on what FooBar does. Be concise as possible.
Who owns FooBar or which team owns it? and/or Who knows the most about it? (link to contributors) or This code is unmaintained and looking for ownership.