Add a linter and code formatter

[mayralgr]

Is your feature request related to a problem? Please describe.
There are several inconsistencies talking about code formatting. In both backend and front-end.

Describe the solution you'd like
Add a linter to the front-end part such as ESLint
Add formatting rules to the backend that could be use to format code such as the Eclipse code formatter plugin (for Eclipse or Intellij) and an xml profile.

Additional context
https://eslint.org/
https://plugins.jetbrains.com/plugin/6546-eclipse-code-formatter
https://imagej.net/Eclipse_code_style_profiles_and_IntelliJ