Doc update: Custom Projection -> Custom Aggregations to avoid duplicate entry

[gfoidl]

Updated the entry in the TOC to match the title of the page.

[gfoidl]

Spell check failed with

ApplicationError: Unsupported NodeJS version (16.20.2); >=18 is required
    at Module.run (file:///opt/hostedtoolcache/node/16.20.2/x64/lib/node_modules/cspell/dist/esm/app.mjs:17:15)
    at file:///opt/hostedtoolcache/node/16.20.2/x64/lib/node_modules/cspell/bin.mjs:6:5
    at ModuleJob.run (node:internal/modules/esm/module_job:193:25)
    at async Promise.all (index 0)
    at async ESMLoader.import (node:internal/modules/esm/loader:530:24)
    at async loadESM (node:internal/process/esm_loader:91:5)
    at async handleMainPromise (node:internal/modules/run_main:65:12) {
  exitCode: 1,
  cause: undefined

So I updated Node to 18.x in 6231402

[mysticmind]

Looks good to me 👍

[gfoidl]

Cool, it's already online 🚀