Patch geojson-flatten version to pass npm audit

[vladkasianenko]

geojson-flatten uses old version of minimist what fails npm audit.

+-- @mapbox/mapbox-gl-draw@1.2.1
| +-- @mapbox/geojson-extent@0.3.2
| | `-- @mapbox/geojson-coords@0.0.0
| |   `-- geojson-flatten@0.2.4
| |     `-- minimist@1.2.0
| `-- @mapbox/geojsonhint@3.0.0
|   `-- minimist@1.2.0

  Low             Prototype Pollution                                           

  Package         minimist                                                      

  Patched in      >=0.2.1 <1.0.0 || >=1.2.3                                     

  Dependency of   @mapbox/mapbox-gl-draw [dev]                                  

  Path            @mapbox/mapbox-gl-draw > @mapbox/geojson-extent >             
                  @mapbox/geojson-coords > geojson-flatten > minimist           



  Low             Prototype Pollution                                           

  Package         minimist                                                      

  Patched in      >=0.2.1 <1.0.0 || >=1.2.3                                     

  Dependency of   @mapbox/mapbox-gl-draw [dev]                                  

  Path            @mapbox/mapbox-gl-draw > @mapbox/geojsonhint > minimist       

  More info       https://npmjs.com/advisories/1179  

Please, update version of geojson-flatten.