gjs-typelib-installer

ddterm depends on multiple GObject libraries (gi:// imports), some of them are often not installed by default.

Instead of silently failing, a notification is shown:

On supported distributions, it has an "Install" button, which installs the requested packages.

gjs-typelib-installer is the backend for it. It implements:

1. require() function that tries to import libraries, and throws MissingDependencies exception if import fails. The exception contains a list of packages that need to be installed to fix the issue.

2. findTerminalInstallCommand() function that finds a working package installation method for the current OS.