meta(mariadb): add mariadb to CI #839

Job	Run time
MySQL (Node 10, Sequelize 5)	7m 49s
MariaDB (Node 10, Sequelize 5)	52s
MySQL (Node 10, Sequelize latest)	8m 20s
MariaDB (Node 10, Sequelize latest)	58s
Postgres (Node 10, Sequelize 5)	9m 51s
SQLite (Node 10, Sequelize 5)	8m 29s
MariaDB (Node 16, Sequelize 5)	53s
SQLite (Node 10, Sequelize latest)	6m 56s
Postgres (Node 10, Sequelize latest)	9m 32s
MySQL (Node 16, Sequelize 5)	7m 31s
SQLite (Node 16, Sequelize 5)	8m 16s
Postgres (Node 16, Sequelize 5)	7m 28s
MySQL (Node 16, Sequelize latest)	10m 29s
SQLite (Node 16, Sequelize latest)	6m 31s
Postgres (Node 16, Sequelize latest)	7m 17s
MariaDB (Node 16, Sequelize latest)	56s
Release	0s
	1h 42m 8s

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