Adds identity matrices to exports

[jmartfrut]

Adds I2, I3, and I4 to the list of exported symbols for the TensorAlgebra module. This makes these identity matrix types directly accessible to users of the library.

[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	main	fb70b85...	main / fb70b85...
Constitutive models/Visco-elastic Ψ	0.0499 ± 0.027 ms	0.0493 ± 0.028 ms	1.01 ± 0.81
Constitutive models/Visco-elastic ∂Ψu	0.0665 ± 0.0064 ms	0.0651 ± 0.0056 ms	1.02 ± 0.13
Constitutive models/Visco-elastic ∂Ψuu	0.116 ± 0.015 ms	0.116 ± 0.015 ms	0.998 ± 0.19
Simulations/StaticMechanicalDirichlet	0.137 ± 0.0082 s	0.136 ± 0.0085 s	1.01 ± 0.088
Simulations/StaticMechanicalNeumann	0.134 ± 0.014 s	0.134 ± 0.016 s	1 ± 0.15
Simulations/ViscoElastic	21.2 s	21.1 s	1
Tensor algebra/Cofactor	0.07 ± 0.01 μs	0.07 ± 0.01 μs	1 ± 0.2
Tensor algebra/Det(A)Inv(A')	0.13 ± 0.01 μs	0.14 ± 0.02 μs	0.929 ± 0.15
Tensor algebra/δδ_λ_2d	30 ± 0 ns	30 ± 0 ns	1 ± 0
Tensor algebra/δδ_μ_2d	30 ± 0 ns	30 ± 0 ns	1 ± 0
time_to_load	2.41 ± 0.014 s	2.43 ± 0.0099 s	0.992 ± 0.0071

Memory benchmarks

	main	fb70b85...	main / fb70b85...
Constitutive models/Visco-elastic Ψ	1.24 k allocs: 0.0777 MB	1.24 k allocs: 0.0777 MB	1
Constitutive models/Visco-elastic ∂Ψu	1.36 k allocs: 0.0898 MB	1.36 k allocs: 0.0898 MB	1
Constitutive models/Visco-elastic ∂Ψuu	2.32 k allocs: 0.155 MB	2.32 k allocs: 0.155 MB	1
Simulations/StaticMechanicalDirichlet	1.51 M allocs: 0.109 GB	1.51 M allocs: 0.109 GB	1
Simulations/StaticMechanicalNeumann	1.48 M allocs: 0.0933 GB	1.48 M allocs: 0.0933 GB	1
Simulations/ViscoElastic	0.343 G allocs: 22 GB	0.343 G allocs: 22 GB	1
Tensor algebra/Cofactor	1 allocs: 0.0781 kB	1 allocs: 0.0781 kB	1
Tensor algebra/Det(A)Inv(A')	4 allocs: 0.25 kB	4 allocs: 0.25 kB	1
Tensor algebra/δδ_λ_2d	0 allocs: 0 B	0 allocs: 0 B
Tensor algebra/δδ_μ_2d	0 allocs: 0 B	0 allocs: 0 B
time_to_load	0.149 k allocs: 11.1 kB	0.149 k allocs: 11.1 kB	1