Release v0.7.0

What's Changed

• update armadillo 12 branch by @conradsnicta in #121
• update to armadillo 12.4.x by @conradsnicta in #122
• add armadillo 12.6.x by @conradsnicta in #124
• add armadillo 12.8.x by @conradsnicta in #127

Full Changelog: v0.6.7...v0.7.0