V2: Add GeneratedFile.array

[timostamm]

GeneratedFile already has the method string() to escape string literals. We already have an internal function for array literals. This promotes it to be a method on GeneratedFile as well.

import { GeneratedFile } from "@bufbuild/protoplugin";

declare f: GeneratedFile;

f.print("const arr = ", f.array([1, 2, 3]), ";");
// const arr = [1, 2, 3];

[timostamm]

Not directly related, but I noticed the docs for the function safeIdentifier need clarification.