feat: Make semantic-release language agnostic

- Do not rely on `package.json` anymore
- Use `cosmiconfig` to load the configation. `semantic-release` can be configured:
  - via CLI options (including plugin names but not plugin options)
  - in the `release` property of `package.json` (as before)
  - in a `.releaserc.yml` or `.releaserc.js` or `.releaserc.js` or `release.config.js` file
  - in a `.releaserc` file containing `json`, `yaml` or `javascript` module
- Add the `repositoryUrl` options (used across `semantic-release` and plugins). The value is determined from CLi option, or option configuration, or package.json or the git remote url
- Verifies that `semantic-release` runs from a git repository
- `pkg` and `env` are not passed to plugin anymore
- `semantic-release` can be run both locally and globally. If ran globally with non default plugins, the plugins can be installed both globally or locally.

BREAKING CHANGE: `pkg` and `env` are not passed to plugin anymore.
Plugins relying on a `package.json` must verify the presence of a valid `package.json` and load it.
Plugins can use `process.env` instead of `env`.

cli.js

@@ -10,6 +10,7 @@ module.exports = async () => {
     .name('semantic-release')
     .description('Run automated package publishing')
     .option('-b, --branch <branch>', 'Branch to release from')
+    .option('-r, --repositoryUrl <repositoryUrl>', 'Git repository URL')
     .option(
       '--verify-conditions <paths>',
       'Comma separated list of paths or packages name for the verifyConditions plugin(s)',
@@ -41,7 +42,7 @@ module.exports = async () => {
       program.outputHelp();
       process.exitCode = 1;
     } else {
-      await require('./index')(program.opts());
+      await require('.')(program.opts());
     }
   } catch (err) {
     // If error is a SemanticReleaseError then it's an expected exception case (no release to be done, running on a PR etc..) and the cli will return with 0