Bump webassets from 0.12.1 to 2.0

[dependabot-preview]

Bumps webassets from 0.12.1 to 2.0.

Changelog

Sourced from webassets's changelog.

2.0 (2019-12-20) Jump to 2.0 to leave alpha versioning and start doing semver. No actual breaking changes.

- Make the `sass` and `scss` filters compatible with the reference compiler
- Add new `sass_ruby` and `scss_ruby` filters to use the deprecated Ruby Sass compiler
- Update and improve a number of filters.
- Add a SRI feature (Arvid Norlander).

Commits

• 44062c8 Update version number.
• 01c8b41 Update CHANGES.
• feb0c30 Merge pull request #525 from amercader/fix-yaml-loader-warning
• a1c273d Use the safe load method in the YAML loader to avoid a warning
• 8380c0d Fix typescript version.
• 8d4a5d6 Merge pull request #521 from VorpalBlade/sri_calculation
• 3b2fc3a Merge pull request #518 from scarabeusiv/patch-1
• 2eae445 Merge pull request #520 from VorpalBlade/unit_test_fixes
• 7d2c789 Merge pull request #523 from leamingrad/new_scss_filter
• 523e826 Merge pull request #524 from jans-forks/update-rjsmin
• Additional commits viewable in compare view

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Dependabot will not automatically merge this PR because this dependency is pre-1.0.0.

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