Update ghpages command to use gh-pages instead of unmaintained ghpages

[vincentfretin]

https://github.com/cvan/ghpages is not maintained (6 vulnerabilities reported) and is just a wrapper to https://github.com/tschaub/gh-pages
Update the command to use gh-pages directly.
I tested the npm run deploy command, that works properly like before.

Before the change:

12 vulnerabilities (1 low, 3 moderate, 6 high, 2 critical)

After the change:

6 vulnerabilities (1 low, 3 moderate, 2 high)
added 11 packages, removed 54 packages, changed 5 packages, and audited 1201 packages in 7s

and then after doing npm audit fix to fix the remaining vulnerabilities:

found 0 vulnerabilities

[dmarcos]

thanks