ci: automate publishing package to npm

[llllvvuu]

Before merging this PR, NPM_TOKEN must be provided to GitHub:

repository > Settings > Secrets and variables > Actions > New repository secret

The NPM_TOKEN can be created at https://www.npmjs.com/

profile pic > Account > Access Tokens > Generate New Token > Granular Access Token

[llllvvuu]

Example run: https://github.com/llllvvuu/vscode-solidity/actions/runs/6282710348/job/17062453049 Example published: https://www.npmjs.com/package/@llllvvuu/vscode-solidity-langserver

[juanfranblanco]

@llllvvuu I saw this, and forgot to mention that pushing automatically to npm is a bit scary with key management.

[llllvvuu]

GitHub Actions secrets are pretty secure, but you could publish manually if you prefer.

[juanfranblanco]

ok I am keeping it open, just in case :)