BZ:2562: https://bugzilla.tianocore.org/show_bug.cgi?id=2562 Add RISCV to "words" section in cspell.base.yaml file to avoid spelling check error. Signed-off-by: Abner Chang <abner.chang@hpe.com> Reviewed-by: Bret Barkelew <bret.barkelew@microsoft.com> Cc: Michael D Kinney <michael.d.kinney@intel.com> Cc: Liming Gao <liming.gao@intel.com>