Add an explanation for emission line S/N in the ETC web app

Tamura-san's comment:

it might be kind if there is a short sentence that S/N of emission line is estimated at every wavelength, somewhere in the part of target section about emission line? That might work for someone like me. Once a user understands what every input means to be used, I presume they can understand outputs no matter how they are presented (or they will search for what they want to see, so will understand them eventually).
 

The tooltip inthe app and document to be modified.