Update the Playwrite Guides articles

[vv-monsalve]

Dave Crossland tweaked a few words of the Playwrite Guides Articles to be more fluent in English (see below).
Now we need to update the About section of the 51 fonts with this change.

Playwrite Guides fonts are single-weight font companions that harmonize seamlessly with their main Playwrite font families. They include guidelines on the baseline, x-height, ascenders, and descenders. These guides provide a visual aid for primary school children that helps young learners grasp the proportions of letterforms and assists them in drawing letters with confidence and accuracy.

Guidelines are present in all characters except for those used for letter/word spacing. To create a versatile tool for teachers when designing practice sheets that feature guidelines without corresponding letters, the underscore is used as a key character. In Playwrite Guides fonts the underscore prints only the guidelines, and matches the width of the normal word space.