build: use npm prepare instead of prepublishOnly

[aloisklink]

In NPM, the prepublishOnly script is run only before running npm publish. However, this means that people trying to use the git version of of this project (i.e. with npm install github:ferdikoomen/openapi-typescript-codegen) won't get a working version of this project, since there will be nothing in the dist/ folder.

NPM (since v4.0.0) supports a prepack script, that is called:

• Runs BEFORE the package is packed
• Runs BEFORE the package is published
• Runs on local npm install without any arguments
• Run AFTER prepublish, but BEFORE prepublishOnly
• NOTE: If a package being installed through git contains a prepare
  script, its dependencies and devDependencies will be installed,
  and the prepare script will be run, before the package is packaged
  and installed.

According to the NPM docs, this is the recommended place to put scripts that do things like "Compiling CoffeeScript source code into JavaScript.".

Fixes #1457, resolves #1458 (this PR is cleaner than that PR)

Benefits

Installing directly from git can be pretty useful, as it allows openapi-typescript-codegen users to use a specific git commit/branch, e.g. so that they don't need to wait for an NPM release (or people can use a commit from a PR that hasn't yet been merged).

Tests

Testing:

• Running directly from GitHub:
  • npx github:ferdikoomen/openapi-typescript-codegen --help (fails)
  • npx github:aloisklink/openapi-typescript-codegen#build/use-npm-prepare-instead-of-prepublishOnly --help (works)
• Built automatically when running npm publish:

  user@pc:~/openapi-typescript-codegen (build/use-npm-prepare-instead-of-prepublishOnly)$ rm -r dist/
  user@pc:~/openapi-typescript-codegen (build/use-npm-prepare-instead-of-prepublishOnly)$         
  npm publish --dry-run
  npm notice 
  npm notice 📦  openapi-typescript-codegen@0.24.0
  npm notice === Tarball Contents === 
  npm notice 1.1kB   LICENSE         
  npm notice 4.3kB   README.md       
  npm notice 2.2kB   bin/index.js    
  npm notice 217.3kB dist/index.js   
  npm notice 4.4kB   package.json    
  npm notice 928B    types/index.d.ts
  npm notice === Tarball Details === 
  npm notice name:          openapi-typescript-codegen              
  npm notice version:       0.24.0                                  
  npm notice filename:      openapi-typescript-codegen-0.24.0.tgz   
  npm notice package size:  33.9 kB                                 
  npm notice unpacked size: 230.3 kB                                
  npm notice shasum:        8b23209515a5e36e1bf9581234f9a8c164e19d3b
  npm notice integrity:     sha512-N7gF1E68WEmrd[...]spGffk8E7DHiQ==
  npm notice total files:   6                                       
  npm notice 
  npm WARN This command requires you to be logged in to https://registry.npmjs.org/ (dry-run)
  npm notice Publishing to https://registry.npmjs.org/ (dry-run)
  + openapi-typescript-codegen@0.24.0

[ferdikoomen]

Good idea! Merged!