igfetchr 0.1.0

• Initial release.
• Core functions: ig_auth, ig_search_markets, ig_get_price, ig_get_historical, ig_get_accounts, ig_logout.
• Added offline testing mode via environment variable IGFETCHR_TESTING = "true" to allow examples and tests to run without network access.
• Includes unit tests, vignette, and examples using mock responses.
• License: GPL-3.