Update install instructions to include dependency of "rollup" npm package

[platymatt]

Request updating the Install instructions to include the "rollup" npm package.

When trying to install the package following the instructions I get this output:

npm install --global @nuwcdivnpt/stigman-watcher
npm error code 127
npm error path /home/anvil/.asdf/installs/nodejs/22.12.0/lib/node_modules/@nuwcdivnpt/stigman-watcher/node_modules/@nuwcdivnpt/stig-manager-client-modules
npm error command failed
npm error command sh -c npx rollup index.js --file index.cjs --format cjs
npm error npm warn exec The following package was not found and will be installed: [email protected]
npm error sh: rollup: command not found