docs: add Building "Build Configs" lightning talk

src/content/config.ts

@@ -25,7 +25,7 @@ const talkCollection = defineCollection({
     description: z.string(),
     events: z.array(
       z.object({
-        date: z.string(),
+        date: z.string().or(z.date()),
         location: z.string().optional(),
         name: z.string(),
         online: z.boolean().optional(),
@@ -38,7 +38,7 @@ const talkCollection = defineCollection({
         ratio: z.string(),
         url: z.string(),
       })
-      .optional(),
+      .optional().or(z.null()),
     title: z.string(),
     video: z
       .object({

src/content/talk/building-build-configs.mdx

@@ -0,0 +1,16 @@
+---
+title: Building "Build Configs"
+description: In this lightning talk, I discuss the "Build Configs" tool I've built to create configuration files.
+speakerdeck: ~
+video: ~
+image: ~
+events:
+  - name: PHP South West (PHPSW)
+    location: Bristol, UK
+    date: 2023-11-08
+    url: https://www.meetup.com/php-sw/events/296917370
+---
+
+"Build Configs" is a tool I've created for creating and managing customised per-project configuration files s such as Docker, Docker Compose, Nix Flake, PHPUnit, and PHPStan.
+
+In this lightning talk, I’ll discuss why I created it, what problem it solves, more about what it does, and how it works.