SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
Often you want to enable and then disable profiling after a period of time.
To make this slightly more ergonomic, add an option to wait for user
input after enabling profiling, this will disable profiling on exit
after the key press.
