Make sprite stacking CSS and markup optional in extract mode

[ShimShamSam]

Do you want to request a feature, report a bug or ask a question?
Feature

What is the current behavior?
Extract mode always includes a <style> tag and markup for sprite stacking.

What is the expected behavior?
An option to turn this off for those who use <svg><use></use></svg> exclusively.

If this is a feature request, what is motivation or use case for changing the behavior?
Apart from the extraneous data in the exported SVG file, my build setup compiles down to a single CSS and JS file which I hash and include as a nonce in my Content Security Policy header. Since this new version now injects an extra <style> tag for sprite stacking, the console throws a silent error that the <style> tag doesn't have an associated nonce in the CSP.

Example:

Refused to apply inline style because it violates the following Content Security Policy directive: "style-src 'sha256-PQmX2D20LVTxXMw/q0RwlgRtaZJZqCjZkLD0q1xzyDY='". Either the 'unsafe-inline' keyword, a hash ('sha256-Kl0oOFCXNACC8wRypDy0qfmAZG1Rd1IPJyGPcb2SthQ='), or a nonce ('nonce-...') is required to enable inline execution.

Please tell us about your environment:

• Node.js version: 7.6.0
• webpack version: 2.6.1
• svg-sprite-loader version: 3.0.3
• OS type & version: Windows 10

[kisenka]

@ShimShamSam I wish you suggest the name of this option.

[ShimShamSam]

spriteStacking (default: true)

Whether or not to include markup to support sprite stacking (allows references to sprites via <img src="icons.svg#my-icon">)

[kisenka]

Related issue JetBrains/svg-mixer#4

[kisenka]

@ShimShamSam sorry for the delay, this feature is shipped in svg-sprite-loader@3.3.0.