project createSourceFile ignores compilerOptions rootDir

**Describe the bug**

Version: `17.0.1`

I want to give my project a baseDir or cwd so all project apis will use it as a relative path
For example, create a project relative to dir `src` so when i call
```ts
project.createSourceFile('test.ts', '');
```
The file will be created under `src/test.ts`

**To Reproduce**

I tried using all of the following compilerOptions props with no luck:

```ts
import { Project } from "ts-morph";

const dir = 'src';

const project = new Project({
compilerOptions: {
rootDir: dir,
baseUrl: dir,
sourceRoot: dir,
rootDirs: [dir]
}
});

project.createSourceFile("test.ts", ``);

project.save
```

**Expected behavior**

I'd expect the `test.ts` file to be created in the `src` directory

Start at the Project.createSourceFile entry point and trace how the supplied file path is resolved against compilerOptions. Reproduce the example with rootDir set to src; done means project.createSourceFile("test.ts", "") creates src/test.ts.

Written by the indexing model from the issue text.