catch and handle errors in GitHub API queries

[elray1]

I think we could insert a tryCatch here to catch errors with calling GitHub API and just return the last cached link date (maybe issuing a warning)

covidData/R/get_time_series_data_link.R

Lines 53 to 57 in b0c64be

	request <- httr::GET(
	'https://api.github.com/repos/CSSEGISandData/COVID-19/commits',
	query = list(path = query_base_file,
	sort = "author-date",
	page = as.character(page)))

the error we're trying to catch is Error in curl::curl_fetch_memory(url, handle = handle) : Timeout was reached: [api.github.com] LibreSSL SSL_read: SSL_ERROR_SYSCALL, errno 60