Merge readFile and readMultipleFiles into a single API

[ykdojo]

This should be ok to do since readMultipleFiles can be used for reading a single file. The new endpoint should be called readFiles.

[ThirDecade2020]

Makes sense & increases efficiency of code. I'd like to work on this one feel free to assign me here.

[ykdojo]

Thank you @ThirDecade2020!