using the samples as documented not functional

[coopernetes]

Describe the bug
Following these steps as documented in the plugin section is not functional in the current version of the sample package. This is caused by incorrect imports from the index.js ESM module-based sample.

Also a slight regression due to #793

Failed to load plugin: Error [ERR_MODULE_NOT_FOUND]: Cannot find package '@finos/git-proxy-plugin' imported from /home/tom/scratch/

To Reproduce
Steps to reproduce the behavior:

$ npm install @finos/git-proxy @finos/git-proxy-plugin-samples
npm warn deprecated [email protected]: Legacy versions of mkdirp are no longer supported. Please update to mkdirp 1.x. (Note that the API surface has changed to use Promises in 1.x.)
npm warn deprecated [email protected]: This package has been decomissioned. See https://github.com/ldapjs/node-ldapjs/blob/8ffd0bc9c149088a10ec4c1ec6a18450f76ad05d/README.md
npm warn deprecated @material-ui/[email protected]: Material UI v4 doesn't receive active development since September 2021. See the guide https://mui.com/material-ui/migration/migration-v4/ to upgrade to v5.
npm warn deprecated @material-ui/[email protected]: Material UI v4 doesn't receive active development since September 2021. See the guide https://mui.com/material-ui/migration/migration-v4/ to upgrade to v5.

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found 0 vulnerabilities

$ cp node_modules/@finos/git-proxy/proxy.config.json .
$ vim proxy.config.json
$ ./node_modules/.bin/git-proxy 
Failed to load plugin: Error [ERR_MODULE_NOT_FOUND]: Cannot find package '@finos/git-proxy-plugin' imported from /home/tom/scratch/
Found 0 plugin modules
creating user
        user=admin,
        gitAccount=none
        [email protected],
        admin=true
HTTP Proxy Listening on 8000
HTTPS Proxy Listening on 8443
Service Listening on 8080

Expected behavior
The samples should load successfully.