docs: Suggestion: unify npm / remove --save from npm install

[muescha]

Summary

Unify npm install commands in docs and all README

Suggested changes:

• 1) remove --save from npm install
• 2) replace npm i with npm install
• 3) put --save-dev as first param after install
  (npm install dep1 dep2 --save-dev -> npm install --save-dev dep1 dep2)
• 4) put commands in code blocks for better copy paste

Motivation

• --save is not anymore needed - see cpmments:

  • Put install in its own code block #22359 (comment)

    laurieontech: --save is no longer necessary for modern versions of npm, but overall this looks like a solid change!

  • fix(docs): improve WordPress tutorial #20520 (comment)

    gillkyle: This brings up a good point as something that might be good to start updating across docs elsewhere.

    npm 5.0.0 was apparently the version to remove the need to add --save which was published more than 3 years ago

• i -> install more easy to know for new users what i means

• --save-dev more visible option

• Putting the install snippet in its own code block makes it easier for people to copy the snippet. I believe this is also consistent with other doc pages. (Put install in its own code block #22359)

Steps to resolve this issue

Draft the doc

• Write the doc, following the format listed in these resources:
  • Overview on contributing to documentation
  • Docs Templates
  • Example of a similar article
• Add the article to the docs sidebar under the [parent doc] section.

Open a pull request

• Open a pull request with your work including the words "closes #[this issue's number]" in the pull request description

[muescha]

it makes sense to have 4 PR after each step?

[marcysutton]

Hi @muescha, separate PRs would be helpful to reviewers. Are you still working on this issue? Thanks for filing it!

[muescha]

I was waiting for an ok before i start

I will do it the next days :)

[mwlai288]

Hi, if this still needs to be worked on, I can help out.