Videos with uppercase extension not recognized

[sebastian-raubach]

First off, thanks for developing this tool, it's been really helpful.

I've got one issue so far though: When dealing with .MP4 files (as generated by many digital cameras), vue coolbox won't recognize it as a video. Looking at the code (https://github.com/lucaspulliese/vue-cool-lightbox/blob/298d8eeef9b0f9e02eb06fd7bd14b34bfbbb575f/src/components/CoolLightBox.vue#L1751) it seems that currently the comparison is done in a case-sensitive way. Maybe changing this to be case insensitive would help solve this.