It's possible to pre-fill the text, but only using the SDK, not with a URL. So, you'd have to write a native extension.
There are plenty of tutorials on using the SDK for this. Here's one:
It has a note at the end about using a URL:
In iOS, you’re allowed to communicate with other apps by using URL. The mobile OS already comes with built-in support of the http, mailto, tel, and sms URL schemes. When you open a HTTP URL, iOS by default launches the URL via Safari. If you want to open the Messages app, you can use the sms URL schedule and specify the recipient. However, such URL scheme doesn’t allow you to put default content.
Keep in mind on iOS there is no way for an app to send an SMS "silently". The user will get the standard iOS SMS dialog, and they will have to hit a button to send. Apple doesn't like "drive-by" SMS! (If you need to do this, you need to use an SMS gateway service.)