Add in ability to recognise functions which load external data

[RobertASmith]

It would be useful for reviewers to see if any of the functions load external data.
This is tricky to recognise because there a lots of different functions that can load data (e.g. read.csv, fread, read_xlsx, loadRDS)
However, a list of the most common ones could at least highlight most data-loaders.
It's fairly simple to do if we are recognising external dependencies anyway.
This could be denoted by highlighting the border of a function in a different colour.

[Smit-tay]

Database and web access should also be considered.

Probably incomplete, but a good starting point:

File
read.csv()
read.table()
read.delim()
read.csv2()
readRDS()
load()
readxl::read_excel()
data.table::fread()
jsonlite::fromJSON()
readr::read_csv()
readr::read_tsv()
readr::read_delim()
haven::read_sas()
haven::read_spss()
haven::read_stata()
arrow::read_parquet()
readLines()
scan()
foreign::read.dta()
foreign::read.spss()
foreign::read.dbf()

Database
DBI::dbConnect()
dbplyr
RODBC::odbcConnect()

Website
httr::GET()
httr::POST()
httr::content()
jsonlite::fromJSON()
xml2::read_xml()