Extensions should store any generated data in a designated extension data directory instead of its installation directory, because installation directory gets purged during extension installation or update.
To get script data directory, use CurrentExtensionDataPath global variable.
To get installation directory of currently running script, use CurrentExtensionInstallPath global variable. In PowerShell scripts you may also use the standard $PSScriptRoot variable.
To get the directory, call GetPluginUserDataPath method. The method returns full path designated to to a specific plugin. The same directory is used to store plugin settings.