get_index_of_optimal_mapping: Get Optimal Mapping Indices
In Benji-Wagner/SequenceMapper: Map Reads to Reference Barcodes

get_index_of_optimal_mapping takes a table of barcodes, a single read, the read's phred score, and the indices of the barcodes that are within a certain Hamming Distance of the read. This function iterates through the indices of the barcodes, calculates the joint probability of the read mapping to the barcode, and then concatenates this value to a vector. Eventually returns a vector of joint probabilities.

1	get_index_of_optimal_mapping(barcodes, read, read_phred, filtered_barcodes)

`barcodes`	A vector of reference barcodes. Each barcode should be of equal length to `read`.
`read`	The read sequence which maps to `barcode`. Should be the same length as `barcode`.
`read_phred`	The phred score for `read`. Should be the same length as `read`.
`filtered_barcodes`	A non-empty vector of integers containing the indices for the barcodes within a certain distance from the read.