Add `allow-scripts`-related checks

[mcmire]

We want to make sure that for a given project:

• The project contains @lavamoat/allow-scripts and @lavamoat/preinstall-always-fail as dev dependencies, and the versions match the same dev dependencies as in the module template.
• The project's package.json contains a lavamoat field with an allowScripts field inside of it, and this file contains "@lavamoat/preinstall-always-fail": false.
• If the project has a .yarnrc.yml (Yarn Modern), then it has a enableScripts: false line; or if the project has a .yarnrc file (Yarn Classic), then it has ignore-scripts true.
  • Note that the module template doesn't have a .yarnrc file. Usually we would stop here and not bother linting the .yarnrc for a project, but in this case, it is critical that each of our projects uses allow-scripts, regardless of which package manager is being used. Among our projects, if they don't use Yarn Modern there is a high likelihood they use Yarn Classic.
• If the project has a .yarnrc.yml file, then .yarn/plugins/@yarnpkg/plugin-allow-scripts.cjs is present and its content matches the same file as in the module template; additionally, .yarnrc.yml's plugins field contains the object { path: ".yarn/plugins/@yarnpkg/plugin-allow-scripts.cjs", spec: "https://raw.githubusercontent.com/LavaMoat/LavaMoat/main/packages/yarn-plugin-allow-scripts/bundles/@yarnpkg/plugin-allow-scripts.js" }.
• If the project has a .yarnrc file (Yarn Classic), then a "setup" package script should be present and should be equal to "yarn install && yarn allow-scripts".

[kanthesha]

There are couple of validation, which seems unnecessary to me.

if the project has a .yarnrc file (Yarn Classic), then it has ignore-scripts true.

I read the why it is required! But once we say the project requires .yarnrc.yml and we need .yarnrc to be absent, then I don't see a point in further validating if there's a .yarnrc then it should have something!!

If the project has a .yarnrc file (Yarn Classic), then a "setup" package script should be present and should be equal to "yarn install && yarn allow-scripts".

Same as above. If we want user to not to have .yarnrc in their project, I don't see a point in if it exists it should have something!!