Google Play has been very clear about this[1]:
> Fund solicitations
> Examples: Donation solicitations from parties without a valid 501(c)(3) tax exempt status clearly displayed to the public; solicitations from parties without valid proof of exempt tax status or proof of registration with the relevant country's regulatory bodies and authorities; and political organizations that have registered with the Federal Election Commission (FEC)
For instance, Wikipedia displays an external "Support Wikipedia" link in the main menu of its Android app[2] without violating Google Play's terms and conditions.