Calling this function in the first chunk of a document will instruct knitr
to automatically log the execution time of each chunk. If using
formatter_glue() or formatter_cli() then the options variable will be
available, providing the chunk options such as chunk label etc.
log_chunk_time(..., level = INFO, namespace = NA_character_)passed to log_level()
see log_levels()
x
# To be put in the first chunk of a document
log_chunk_time("chunk {options$label}")