Fix parsing for timestamps with commas as decimal seperators

[Dananji]

Related issue: #539

SRT allows commas as decimal separators in the timestamps. e.g.

17
00:00:42,540 --> 00:00:45,420
We provide uncompromising quality,

When using content search on these transcripts in Avalon's search response is formatted as follows;

 id: "https://avalon-dev.dlib.indiana.edu/media_objects/g158bh28p/manifest/canvas/2f75r800tsearch/0cb75a80-062e-4315-b361-144f6af7f958",
 type: "Annotation",
 motivation: "supplementing",
 body: {
   type: "TextualBody",
   value: "<em>We</em> provide uncompromising quality,",
   format: "text/plain",
 },
 target: "https://avalon-dev.dlib.indiana.edu/master_files/2f75r800t/supplemental_files/298transcripts#t=00:00:42.540,00:00:45,420"

The timestamps contain multiple commas, which resulted in incorrect timestamps when parsing the response.

[cjcolvar]

Looks good!