[nu-cmd-base] add missing LICENSE text (#10855) #224

Job	Run time
std-lib-and-python-virtualenv (ubuntu-20.04, py)	8m 13s
fmt-clippy (windows-latest, default)	9m 28s
std-lib-and-python-virtualenv (macos-latest, py)	9m 44s
tests (windows-latest, default)	19m 54s
fmt-clippy (windows-latest, extra)	9m 38s
std-lib-and-python-virtualenv (windows-latest, py)	12m 57s
tests (macos-latest, default)	12m 40s
fmt-clippy (macos-latest, default)	4m 7s
tests (ubuntu-20.04, default)	8m 25s
fmt-clippy (macos-latest, extra)	6m 36s
tests (ubuntu-20.04, dataframe)	10m 44s
plugins (windows-latest)	12m 2s
fmt-clippy (ubuntu-20.04, default)	3m 48s
tests (ubuntu-20.04, extra)	8m 12s
plugins (macos-latest)	5m 16s
fmt-clippy (ubuntu-20.04, dataframe)	5m 45s
plugins (ubuntu-20.04)	3m 25s
fmt-clippy (ubuntu-20.04, extra)	4m 8s
	2h 35m 2s

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