If you're reading this, you're probably the sole individual directly responsible for the continued maintenance of this website!
Some pointers:
You can hire web devs to help you! First-years are probably your best bet; they're still early into their university careers, and they're often really amenable to opportunities to gain any exposure at all to web development.
If you choose to do so, make sure that there's work for everyone to do. Unless you're working on a major overhaul, this probably means you only want to hire a couple of developers. When making hiring decisions, consider that about 50% of the people you bring in will disappear indefinitely come midterm season.
If I've set things up right, you should have a non-voting seat at MathSoc Board. You probably won't need to use this; it's moreso intended as a MathSoc policy-friendly way to lock you in to this position for several terms at once. You're welcome!
If ever you need to change something about the position however - something relating to the role of the webmaster, or how MathSoc works at a wider scale, you should be able to submit a motion through your position as a member of board. If not, just ask someone to do it on your behalf!
This one's hard. The webmaster has a little bit more ability to break things in dramatic ways, or freeze parts of MathSoc operations, than other roles. Try to find someone who 1) is well-known to be trustworthy and reliable, 2) is reasonably capable in web development, and 3) will be around for the full length of the webmaster term. Prioritize them in that order; a reliable rookie is preferable to an expert that will ghost.
You may be asked to prepare transition notes for the next person. Do so in this repository, and don't consider them "transition notes." Making the contents public will make them harder to lose later on. In terms of contents, just make sure that any tribal knowledge you've collected over the years is written down, and ensure that you are accessible to the next person in the role.
I don't really have much more advice here. Good luck. Hopefully, you can find someone to tap on the shoulder and convince to take on the role. If not, run into the woods. I hear Thunder Bay is nice this time of year.