impossible to install package from npm

[tidiview]

there must be a problem: not found.

[tidiview]

error log. For yarn, then npm.

PS C:\xampp\htdocs\francois-vidit-2-15.com-svelte-navaid> yarn add svelte-relay
yarn add v1.22.4
[1/4] Resolving packages...
error An unexpected error occurred: "https://registry.yarnpkg.com/svelte-relay: Not found".
info If you think this is a bug, please open a bug report with the information provided in "C:\\xampp\\htdocs\\francois-vidit-2-15.com-svelte-navaid\\yarn-error.log".
info Visit https://yarnpkg.com/en/docs/cli/add for documentation about this command.
PS C:\xampp\htdocs\francois-vidit-2-15.com-svelte-navaid>
                                                          npm install
npm notice created a lockfile as package-lock.json. You should commit this file.
npm WARN rollup-plugin-terser@6.1.0 requires a peer of rollup@^2.0.0 but none is installed. You must install peer dependencies yourself.

added 1 package from 1 contributor, removed 1 package, updated 122 packages and audited 123 packages in 9.176s

15 packages are looking for funding
  run `npm fund` for details

found 0 vulnerabilities

PS C:\xampp\htdocs\francois-vidit-2-15.com-svelte-navaid> npm install svelte-relay
npm ERR! code E404
npm ERR! 404 Not Found - GET https://registry.npmjs.org/svelte-relay - Not found
npm ERR! 404
npm ERR! 404  'svelte-relay@latest' is not in the npm registry.
npm ERR! 404 You should bug the author to publish it (or use the name yourself!)
npm ERR! 404
npm ERR! 404 Note that you can also install from a
npm ERR! 404 tarball, folder, http url, or git url.

npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Users\François\AppData\Roaming\npm-cache\_logs\2020-06-18T10_51_00_767Z-debug.log
PS C:\xampp\htdocs\francois-vidit-2-15.com-svelte-navaid>

[kesne]

Yeah they're not yet published

[tidiview]

So how can I use relay?

[kesne]

Alright I published the packages

[tidiview]

ok I've been able to install packages: thanks ☆