cpu-monitor-text@gnemonix : Improve percentage display so applet width does not change

[DoneWorkin]

Applet name and maintainer

cpu-monitor-text@gnemonix @gnemonix

What would you like to see?

When the CPU percentage changes number of digits the width of the applet changes and moves things around.
Improve the functionality by padding the percentage with Figure Space characters.

Suggested code change to _pad function as follows (will attempt to create pull request for this)

    _pad: function(percent) {
        let str = percent.toString();
        let str_length = this.max_percentage.toString().length;
        
        while(str.length < str_length) {
            str = "\u2007" + str;
        }
        return (str);
    },