How do I fix has unmet peer dependency...

…and what does it even mean?

DEBUG [40866a5f] 	yarn install v1.7.0
DEBUG [40866a5f] 	warning package.json: No license field
DEBUG [40866a5f] 	warning No license field
DEBUG [40866a5f] 	[1/4] Resolving packages...
DEBUG [40866a5f] 	[2/4] Fetching packages...
DEBUG [40866a5f] 	info fsevents@1.2.4: The platform "linux" is incompatible with this module.
DEBUG [40866a5f] 	info "fsevents@1.2.4" is an optional dependency and failed compatibility check. Excluding it from installation.
DEBUG [40866a5f] 	[3/4] Linking dependencies...
DEBUG [40866a5f] 	warning "@rails/webpacker > postcss-cssnext@3.1.0" has unmet peer dependency "caniuse-lite@^1.0.30000697".
DEBUG [40866a5f] 	warning " > react-google-maps@9.4.5" has unmet peer dependency "@types/googlemaps@^3.0.0".
DEBUG [40866a5f] 	warning " > react-google-maps@9.4.5" has unmet peer dependency "@types/markerclustererplus@^2.1.29".
DEBUG [40866a5f] 	warning " > react-google-maps@9.4.5" has unmet peer dependency "@types/react@^15.0.0 || ^16.0.0".
DEBUG [40866a5f] 	warning " > webpack-dev-server@2.11.2" has unmet peer dependency "webpack@^2.2.0 || ^3.0.0".
DEBUG [40866a5f] 	warning "webpack-dev-server > webpack-dev-middleware@1.12.2" has unmet peer dependency "webpack@^1.0.0 || ^2.0.0 || ^3.0.0".
DEBUG [40866a5f] 	[4/4] Building fresh packages...
DEBUG [40866a5f] 	Done in 17.33s.

Firstly the licence warning can be removed by making the package private.

{
  "private": true,
  "dependencies": {
    "@rails/webpacker": "3.5",
    "axios": "^0.18.0",
    "babel-preset-react": "^6.24.1",
  /*... and some more ... */
}