Insert usepackage correctly

[PHPirates]

Fixes #1274

Summary of additions and changes

• Insert in PSI tree instead of document

How to test this pull request

• Use quickfix of any command/environment which requires a package

[slideclimb]

Works, but the environment requires ... package inspection is broken? When using an amsmath environment in an \inputed file, it keeps showing the inspection and adds multiple \usepackage{amsmath} to the main file.