`insertleftunit`, `insertrightunit` and `removeunit` #378

Job	Run time
Julia 1 - ubuntu-latest - x64	11m 57s
Julia 1 - macOS-latest - x64	9m 39s
Julia 1 - windows-latest - x64	12m 47s
Julia lts - ubuntu-latest - x64	8m 41s
Julia lts - macOS-latest - x64	7m 57s
Julia lts - windows-latest - x64	9m 23s
Julia nightly - ${{ matrix.os }} - ${{ matrix.arch }}	0s
	1h 0m 24s

Provide feedback