Replace any type with ExecOptions for type safety in vale-runner

[Copilot]

Addresses type safety feedback from PR #11 where execOptions was typed as any, bypassing TypeScript's type checking.

Changes:

• Import ExecOptions from child_process module
• Type execOptions object with ExecOptions instead of any

// Before
import { exec } from "child_process";
const execOptions: any = {
  encoding: 'utf-8',
  cwd: process.cwd()
};

// After
import { exec, ExecOptions } from "child_process";
const execOptions: ExecOptions = {
  encoding: 'utf-8',
  cwd: process.cwd()
};

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