Assorted codes for checking completion speed.

• :so timings.vim
• <leader>T to start recording delays between InsertCharPre and CompleteChanged
• type some code
• <leader>T to stop recording delays
• :TimingsSave examples/cmp-timings.json nvim-cmp to export timings with a given title
• $julia -i -- timings.jl examples/coc-timings.json examples/cmp-timings.json to plot timing series
• call timings(ARGS) from Julia REPL to refresh plots for updated data