Add README-related checks

[mcmire]

For a given project, we want to ensure that:

• The project has a README.md. Past this, we want to ensure that:
  • It has a single, non-empty H1.
  • It has at least these H2 headers with non-empty content, in this order: "Installation", "Usage", "Contributing".
  • The "Contributing" section has at least a "Setup" section, headered by an H3, with non-empty content.
  • The "Setup" section has only a bulleted list with three items.
  • The first item in the "Setup" section matches Install [Node ${version}](https://nodejs.org) if .nvmrc exists and is not lts/*, otherwise it matches Install the current LTS version of [Node.js](https://nodejs.org).
  • The second item in the "Setup" section matches Install [Yarn Modern](https://yarnpkg.com/getting-started/install) if packageManager exists in package.json and matches yarn@<version> and the version is >= 2; otherwise it matches Install [Yarn Classic](https://classic.yarnpkg.com/en/docs/install).
  • The third item in the "Setup" section matches Run `yarn setup` to install dependencies and run any required post-install scripts if package.json has a setup script; otherwise Run `yarn install` to install dependencies and run any required post-install scripts.
  • The "Contributing" section has a "Testing and Linting" section following "Setup", headered by an H3, if package.json contains either a test script or a lint script.
  • The "Testing and Linting" section (if present) should have the sentence Run `yarn test` to run the tests once. if the test script exists.
  • The "Testing and Linting" section (if present) should have the sentence To run tests on file changes, run `yarn test:watch`. if the test:watch script exists.
  • The "Testing and Linting" section (if present) should have the sentence Run `yarn lint` to run the linter. if the lint script exists.
  • The "Testing and Linting" section (if present) should have the sentence Run `yarn lint:fix` to run the linter and fix any automatically fixable issues if the lint script exists.
  • The "Contributing" section has a "Release & Publishing" section following "Setup" and optionally "Testing and Linting" if we can find uses: MetaMask/action-npm-publish, uses: MetaMask/action-publish-release, and uses: MetaMask/action-create-release-pr among the project's GitHub workflow files. The content of this should match the same section as in the module template. (We could make this smarter, but all of these workflows go together.)

[mcmire]

In order to work on this ticket, we will probably have to parse the README using a Markdown parser. I am thinking remark or markdown-it, but there may be others. I might create a new research ticket for this if we feel the need.

[mcmire]

Also note that there is some overlap between this ticket and #12, in that we already have a rule which looks for Node installation instructions in the README. We may want to tweak this rule, however, to account for whichever version is listed in .nvmrc and/or lack of .nvmrc.