The current implementation felt a bit ad-hoc and notably allowed
textContent to operate on all node types. It also only returned the
child text content of the Node instead of the descendant text content.
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 *
