fix: move values to .env

[jmolivas]

fix: move values to .env

[jmolivas]

This can be set on the content itself

`gist:jmolivas/8bc5ab0c504c804451d3c5a9dc56a303#try-umami-sqlite.yml`

Where jmolivas is the gist owner

[jmolivas]

We can remove from the gastby-config.js file

          {
            resolve: 'gatsby-remark-embed-gist',
            options: {
              username: 'jmolivas',
              includeDefaultCss: true
            }
          },

[jmolivas]

Fixed with #5