Singular.jl 0.18.9 released

Today Singular.jl 0.18.9 has been released.

Diff since v0.18.8

Merged pull requests:

• Update julia versions in CI (#678) (@lgoettgens)
• Rename invalidations CI test (#679) (@fingolfin)
• add set_randomseed to libsingular_julia (#680) (@hannes14)
• divrem with flag complete_reduction (#681) (@hannes14)
• complete_reduction for reduce (#682) (@hannes14)
• divrem for smodule (#684) (@hannes14)
• Check dim of shifts in hilbert_series (#686) (@JohnAAbbott)
• Update to latest libsingular_julia (#687) (@fingolfin)
• new release v0.18.9 (#688) (@ederc)