Root mean squared logarithmic error (RMSLE) is the square root of msle().
Details
$$\mathrm{RMSLE}=\sqrt{\frac{1}{n}\sum_{i=1}^n [\log(1+obs_i)-\log(1+pred_i)]^2}.$$
RMSLE is non-negative and zero is ideal. It has the same non-negative input
requirement and log1p convention as msle(), returning NA with a warning
when either input contains a negative value. Missing-value handling follows
bias().
References
Hodson (2022). See msle().
