implemented merge-sort in js with test cases#105

ignacio-chiazzo merged 1 commit intoignacio-chiazzo:masterignacio-chiazzo/Algorithms-Leetcode-#"/Franklin-017/Algorithms-Leetcode-Javascript/tree/merge-sort" aria-describedby=":Rdsn1d:">Franklin-017:merge-sortFranklin-017/Algorithms-Leetcode-#"IconButton" type="button" data-loading="false" data-no-visuals="true" data-size="small" data-variant="invisible" aria-describedby=":Rtlsn1d:-loading-announcement" aria-labelledby=":Rlsn1d:">Copy head branch name to clipboard