Add types MVec3, PosVector, VelVector #11

Job	Run time
Julia 1.10 - ubuntu-latest - x64 - pull_request	2m 26s
Julia 1 - ubuntu-latest - x64 - pull_request	4m 8s
Julia pre - ubuntu-latest - x64 - pull_request	4m 15s
Julia 1 - windows-latest - x64 - pull_request	5m 31s
Julia 1 - macOS-latest - x64 - pull_request	7m 7s
	23m 27s

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