Add IpHeadersSlice and IpSlice::header()#136

xyzzyz wants to merge 1 commit intoJulianSchmid:masterJulianSchmid/etherparse:masterfrom

xyzzyz:amichalik/ipheaders-from-slicexyzzyz/etherparse:amichalik/ipheaders-from-sliceCopy head branch name to clipboard