Update dependency rollup to ^2.13.1

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
rollup (source)	devDependencies	minor	^2.12.0 -> ^2.13.1

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Release Notes

rollup/rollup

### [`v2.13.1`](https://togithub.com/rollup/rollup/blob/master/CHANGELOG.md#​2131) [Compare Source](https://togithub.com/rollup/rollup/compare/v2.13.0...v2.13.1) _2020-06-04_ ##### Bug Fixes - Prevent conflicts in SystemJS when `module` is used as a top-level variable ([#​3614](https://togithub.com/rollup/rollup/issues/3614)) ##### Pull Requests - [#​3614](https://togithub.com/rollup/rollup/pull/3614): Handle system reserved identifier dedupes ([@​guybedford](https://togithub.com/guybedford)) ### [`v2.13.0`](https://togithub.com/rollup/rollup/blob/master/CHANGELOG.md#​2130) [Compare Source](https://togithub.com/rollup/rollup/compare/v2.12.1...v2.13.0) _2020-06-03_ ##### Features - Allow to specify that an emitted chunk is only loaded after a given module has loaded to improve chunking ([#​3606](https://togithub.com/rollup/rollup/issues/3606)) ##### Pull Requests - [#​3606](https://togithub.com/rollup/rollup/pull/3606): Enable specifying implicit dependencies when emitting chunks ([@​lukastaegert](https://togithub.com/lukastaegert)) ### [`v2.12.1`](https://togithub.com/rollup/rollup/blob/master/CHANGELOG.md#​2121) [Compare Source](https://togithub.com/rollup/rollup/compare/v2.12.0...v2.12.1) _2020-06-02_ ##### Bug Fixes - Render valid imports when chunk names correspond to directory names in virtual setups ([#​3609](https://togithub.com/rollup/rollup/issues/3609)) ##### Pull Requests - [#​3609](https://togithub.com/rollup/rollup/pull/3609): Handle imports from chunks with names that correspond to parent directory names of other chunks ([@​guybedford](https://togithub.com/guybedford))

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