Right clicking on back or forward will now show a context menu with
URLs to navigate to. Also added an optional argument for the number of
steps in go_back() and go_forward().
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 *
