#2029: Completely replace yarn with npm commands throughout the project

[KonstantinEpam23]

closes #2029 #2030 #2031 #2008

[AnastasiiaPlyako]

I think we also can update read.me files in packages/ketcher-core etc

[KonstantinEpam23]

I think we also can update read.me files in packages/ketcher-core etc

Well, for people who use our packages as npm modules - we don't really care if they use npm or yarn, they should work for both. These changes are mainly for people who work with the repository directly (like us 😄 )

[papillot]

Thank-you for looking into this. For what it's worth, I've tried to run npm install using this branch (npm install --save "https://github.com/epam/ketcher.git#2029-completely-replace-yarn-with-npm-commands-throughout-the-project") and it ultimately failed at the post-install step where husky install is invoked, because husky is not part of the regular dependencies.
Here is the relevant part of the npm install logs:

329 error command failed
330 error command sh -c husky install
331 error sh: husky: command not found

[KonstantinEpam23]

Hello @papillot , thank you checking this PR and pointing this out! I believe you are correct about the reason that the error appears b/c the library is not part of the non-dev builds.
Currently ketcher is mostly oriented on using its separate packages (ketcher-core, ketcher-react, etc) and building your own app (e.g. using the /example or /demo directories from the repository)

In the future we may be looking to avoiding using husky for non-dev builds.
Hopefully this clarifies things a bit, thank you for your input again!