TestProblems not defined

[ranocha]

Running the example from https://juliagni.github.io/GeometricIntegrators.jl/stable/integrators/

julia> using GeometricIntegrators

julia> ode = TestProblems.HarmonicOscillatorProblem.harmonic_oscillator_ode()
ERROR: UndefVarError: TestProblems not defined
Stacktrace:
 [1] top-level scope at REPL[2]:1

[ranocha]

Additionally, I get

julia> harmonic_oscillator_iode
ERROR: UndefVarError: harmonic_oscillator_iode not defined

following the same page of the docs

[michakraus]

I forgot to update the docs when extracting the example code into GeometricProblems.jl
All examples should work now, cf. https://juliagni.github.io/GeometricIntegrators.jl/latest/integrators/