fix(custom-protocol): SVG mime type - close #168

[lemarier]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Documentation
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes. Issue #___
• No

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g. fix: #xxx[,#xxx], where "xxx" is the issue number)
• A change file is added if any packages will require a version bump due to this PR per the instructions in the readme.

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:

Fix SVG mime type. Tested on macOS. Need more tests on Windows and linux.

[nothingismagick]

OMG this is so my bad. I actually participated in some W3C discussions about this and used my "rather have it this way" glasses than the way it really is.

[wusyong]

Tested on windows and linux and it's working