Route regexes parsing with adjacent ] [

[Nokorbis]

Describe the bug
In route regex,
when you use multiple [classes], there needs to be a "separator" between classes to make the route regex works.

Workaround
Separating adjacent ][ with "{1}"
exemple : [0-2]{1}[0-9]{1}-[0-5]{1}[0-9]{1}

Logs

To Reproduce
Create a route with the pattern : [time([0-2][0-9]-[0-5][0-9])]
and run the sapper server

Expected behavior
Makes sapper support this regex

Stacktraces

Information about your Sapper Installation:

• The output of npx envinfo --system --npmPackages svelte,sapper,rollup,webpack --binaries --browsers
  System:
  OS: Windows 10 10.0.18363
  CPU: (12) x64 Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz
  Memory: 16.26 GB / 31.82 GB
  Binaries:
  Node: 12.10.0 - F:\Dev\SDKs\nodejs\node.EXE
  Yarn: 1.17.3 - F:\Dev\SDKs\yarn\bin\yarn.CMD
  npm: 6.14.7 - F:\Dev\SDKs\nodejs\npm.CMD
  Browsers:
  Chrome: 84.0.4147.105
  Edge: Spartan (44.18362.449.0)
  Internet Explorer: 11.0.18362.1
  npmPackages:
  rollup: ^2.23.0 => 2.23.0
  sapper: ^0.27.16 => 0.27.16
  svelte: ^3.24.0 => 3.24.1

Severity
Minor