Add extended key property to `SLIP10Node` #126

Job	Run time
Check workflows	6s
Build, lint, and test / Prepare	13s
Build, lint, and test / Test (16.x)	1m 48s
Build, lint, and test / Build	22s
Build, lint, and test / Lint	33s
Build, lint, and test / Test (18.x)	1m 53s
Build, lint, and test / Compatibility test (16.x)	2m 19s
Build, lint, and test / Test (20.x)	1m 31s
Build, lint, and test / Compatibility test (20.x)	2m 6s
All jobs completed	1s
All jobs pass	1s
is-release	0s
Publish release	0s
	10m 53s

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