ERROR #98123 WEBPACK Generating development JavaScript bundle failed on `gatsby develop`

The issues are quite self-explanatory:

/home/myPC/Documents/blog/src/components/Feed/Feed.js
  4:13  error  Parsing error: Unexpected token {
✖ 1 problem (1 error, 0 warnings)

File: src/components/Feed/Feed.js

/home/myPC/Documents/blog/src/components/Icon/Icon.js
  5:6  error  Parsing error: Unexpected token Props

✖ 1 problem (1 error, 0 warnings)

File: src/components/Icon/Icon.js

And so on...

As you can see in their repository, you must use yarn instead of npm since the dependencies are lock using yarn.lock file.

So, remove your node_modules, your cache folder and run yarn install(you may need to install it before).