Add types MVec3, PosVector, VelVector #12

Job	Run time
Julia 1.10 - ubuntu-latest - x64 - pull_request	2m 21s
Julia 1 - ubuntu-latest - x64 - pull_request	4m 7s
Julia pre - ubuntu-latest - x64 - pull_request	4m 13s
Julia 1 - windows-latest - x64 - pull_request	5m 24s
Julia 1 - macOS-latest - x64 - pull_request	6m 14s
	22m 19s

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