If we want to write such a thing let's define compassion: "Compassion is an understanding of the emotional state of another or oneself. Not to be confused with empathy, compassion is often combined with a desire to alleviate or reduce the suffering of another or to show special kindness to those who suffer." Compassion is really about showing up. It is the ability to hold space for ourselves and others as we live what it is to be human.
In considering a Charter for Compassion, a global map as it were for guiding us to be compassionate, I feel we must all strive to exist in this state of being present, and constant vigilance of our motivations for doing, caring, believing. Compassionate behavior can slip into rescuing or condescension, or be driven by guilt, shame, or fear. That would be ultimately counter productive. So in order to breed true compassion we must begin to work our way out from under many cultural constraints which have been imposed over centuries to control human behavior. Step number one: learn to show up in the present moment for each moment. It might only be for a few seconds at first almost like surfacing for air while swimming. But with practice soon we might begin to float with ease.