browser: add method to retrieve server version

[stoyanov-kaloyan]

Added a version method to retrieve Ollama server version. It fetches it from /api/version

Usage:

import { Ollama } from 'ollama'

const ollama = new Ollama({ host: 'http://127.0.0.1:11434' })
const res = await ollama.version()

Addresses #258

[BruceMacD]

Thanks!