hoppet v2 release note

We document the three main new features in the v2 release series of the hoppet parton distribution function evolution code, specifically support for N <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mrow></mml:mrow> <mml:mrow></mml:mrow> <mml:mn>3</mml:mn></mml:mmultiscripts> </mml:math> LO QCD evolution in the variable flavour number scheme, for the determination of hadronic structure functions for massless quarks up to N <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mrow></mml:mrow> <mml:mrow></mml:mrow> <mml:mn>3</mml:mn></mml:mmultiscripts> </mml:math> LO, and for QED evolution to an accuracy phenomenologically equivalent to NNLO QCD. Additionally we describe a new Python interface, CMake build option, functionality to save a hoppet table as an LHAPDF grid and update our performance benchmarks, including optimisations in interpolating PDF tables.