Uploaded SVG as a image

When user drag file into textarea for comment, GitLab will upload it and insert image or link into textarea.

Currently SVG files are treat as a file, so only link to file will be inserted: [file.svg](/path/to/file.svg)

Almost all browsers support SVG in <img>, so there is no problem to insert it as a image: ![file.svg](/path/to/file.svg)