[CI] Upgrade all NPM pksg, gulp to v5, add check-markdown wrapper as workaround

[chalin]

• OMG, finally fixed this by working around issues with Gulp 5. I just can't get Gulp 5 (which now uses chokidar) to ignore symlinks. The workaround implemented here is to create a bogus symlink target if it doesn't exist.
• Closes Bump gulp from 4.0.2 to 5.0.0 #4225
• Closes Update pkgs Hugo to 0.127.0 and more #4633

Here's the workaround in action, from https://github.com/open-telemetry/opentelemetry.io/actions/runs/9428586176/job/25974087551?pr=4233:

Run npm run check:markdown

> check:markdown
> scripts/check-markdown-wrapper.sh

WARNING: required symlink target does not exist, creating it: content-modules/opentelemetry-go/example
+ mkdir -p content-modules/opentelemetry-go/example
+ exec npm run _check:markdown

> _check:markdown
> npx gulp lint-md

[12:08:19] Using gulpfile ~/work/opentelemetry.io/opentelemetry.io/gulpfile.js
[12:08:20] Starting 'lint-md'...
Processed [4](https://github.com/open-telemetry/opentelemetry.io/actions/runs/9428586176/job/25974087551?pr=4233#step:6:5)48 files, 0 had issues.
[12:08:23] Finished 'lint-md' after 3.[6](https://github.com/open-telemetry/opentelemetry.io/actions/runs/9428586176/job/25974087551?pr=4233#step:6:7)9 s

[chalin]

Waiting on:

• [CI] Ensure check-text GHA jobs use proper node version #4235

[cartermp]

/fix:all

[github-actions]

You triggered fix:all action run at https://github.com/open-telemetry/opentelemetry.io/actions/runs/8533808146

[chalin]

Works locally, and on GitPod, but not under GH actions :-/ ... will need to investigate further when I have the time. Putting in draft in the meantime.

[chalin]

Finally all green! Merging ✨