Update tokens.md
Update tokens.md

Renames 'issuer' to 'iss'
jitsi/lib-jitsi-meet,dmurtari/lib-jitsi-meet,damencho/lib-jitsi-meet,jitsi/lib-jitsi-meet,dmurtari/lib-jitsi-meet,jiyeyuran/lib-jitsi-meet,nevermind-corp/ljm,adambowles/lib-jitsi-meet,adambowles/lib-jitsi-meet