If you mean "also," use "also." I don't know if you're the author, but regardless, composing based on your perception of the way your audience thinks assumes too much about your audience and their perceptions of the issues you're writing around without being clear.
Here is the only gendered sentence in the entire OP:
> So to all the girls learning how to code, and not sure where you stand: screw it, and just call yourself a developer already.
Is it really so insulting that she didn't say, "girls and boys"? There are only two other gendered words, and they're both pronouns referring to a specific individual.
And such a reminder would be completely appropriate. If someone else didn't remind him, then you should step up and do so yourself.
Agree. There's nothing in the article that even suggests that this phenomenon only applies to, or more often applies to women.
The "to all the girls" part is clearly due to the fact that the article is written by a woman and posted on a site mostly directed towards women.
EDIT: It looks like the article's been edited since it was originally posted, and that it used the wording "this experience applies to women (...)." I still don't think this is a major issue since the article was meant to assuage the concerns of someone who's experiencing impostor syndrome, and again, the article is written by a woman and posted on a site mostly directed towards women.