fix: use ESM import for tailwindcss-animate in config

[jcwilk]

I ran into what was (at least on my machine) a bug when trying to hit the frontend after setup:

> brian-frontend@0.1.0 dev /home/user/workspace/brian/frontend
> vite


  VITE v7.3.1  ready in 184 ms

  ➜  Local:   http://localhost:5173/
  ➜  Network: use --host to expose
file:///home/user/workspace/brian/frontend/tailwind.config.js:93
  plugins: [require("tailwindcss-animate")],
           ^

ReferenceError: require is not defined
    at file:///home/user/workspace/brian/frontend/tailwind.config.js:93:12
    at ModuleJobSync.runSync (node:internal/modules/esm/module_job:395:35)
    at ModuleLoader.importSyncForRequire (node:internal/modules/esm/loader:329:47)
    at loadESMFromCJS (node:internal/modules/cjs/loader:1414:24)
    at Module._compile (node:internal/modules/cjs/loader:1547:5)
    at Object..js (node:internal/modules/cjs/loader:1677:16)
    at Module.load (node:internal/modules/cjs/loader:1318:32)
    at Function._load (node:internal/modules/cjs/loader:1128:12)
    at TracingChannel.traceSync (node:diagnostics_channel:322:14)
    at wrapModuleLoad (node:internal/modules/cjs/loader:219:24)
    at Module.require (node:internal/modules/cjs/loader:1340:12)
    at require (node:internal/modules/helpers:138:16)
    at /home/user/workspace/brian/frontend/node_modules/.pnpm/tailwindcss@3.4.19/node_modules/tailwindcss/lib/lib/load-config.js:51:20
    at loadConfig (/home/user/workspace/brian/frontend/node_modules/.pnpm/tailwindcss@3.4.19/node_modules/tailwindcss/lib/lib/load-config.js:55:6)
    at getTailwindConfig (/home/user/workspace/brian/frontend/node_modules/.pnpm/tailwindcss@3.4.19/node_modules/tailwindcss/lib/lib/setupTrackingContext.js:74:116)
    at /home/user/workspace/brian/frontend/node_modules/.pnpm/tailwindcss@3.4.19/node_modules/tailwindcss/lib/lib/setupTrackingContext.js:103:92
    at /home/user/workspace/brian/frontend/node_modules/.pnpm/tailwindcss@3.4.19/node_modules/tailwindcss/lib/processTailwindFeatures.js:46:11
    at plugins (/home/user/workspace/brian/frontend/node_modules/.pnpm/tailwindcss@3.4.19/node_modules/tailwindcss/lib/plugin.js:38:69)
    at LazyResult.runOnRoot (/home/user/workspace/brian/frontend/node_modules/.pnpm/postcss@8.5.6/node_modules/postcss/lib/lazy-result.js:361:16)
    at LazyResult.runAsync (/home/user/workspace/brian/frontend/node_modules/.pnpm/postcss@8.5.6/node_modules/postcss/lib/lazy-result.js:290:26)
    at LazyResult.async (/home/user/workspace/brian/frontend/node_modules/.pnpm/postcss@8.5.6/node_modules/postcss/lib/lazy-result.js:192:30)
    at LazyResult.then (/home/user/workspace/brian/frontend/node_modules/.pnpm/postcss@8.5.6/node_modules/postcss/lib/lazy-result.js:436:17)

Node.js v22.12.0
 ELIFECYCLE  Command failed with exit code 1.
 ```
 
 All the different ways to import/require things make my head spin at times :sweat_smile: this variant fixed it for me, happy to provide more info about my system (ubuntu 24.04) if you're not able to reproduce.