Add ScopeLink (Astrolabs) driver documentation

[tothbastrolabs]

Documentation for the ScopeLink telescope controller from Astrolabs, driver indi_scopelink.

Requested by @knro on indilib/indi-3rdparty#1371, where the driver is under
review; the page was written as that submission's doc/index.md and is removed from the driver tree in
the same round.

What is here

src/content/docs/focusers/astrolabs/scopelink/
├── scopelink.md          the page
├── scopelink.yaml        metadata
├── scopelink.webp        thumbnail, 300x300
└── images/               11 screenshots, 1180x700
public/images/manufacturers/astrolabs.webp

focusers is the primary category because that is the driver's devGroup in indi_scopelink.xml. The
page is listed under dust caps, light boxes and auxiliaries as well: the driver publishes a single device
that claims FOCUSER_INTERFACE, LIGHTBOX_INTERFACE and AUX_INTERFACE, adding DUSTCAP_INTERFACE
once the front flap's travel is calibrated. Happy to trim that list if fewer is preferred.

The page covers installation, connecting, every tab of the control panel with a screenshot taken from the
real generation 3 controller, the driver's simulation mode, troubleshooting and what to include in a bug
report.

Notes

• Screenshots are lossless WebP (magick x.png -define webp:lossless=true x.webp) — pixel-exact and
  about half the size of the PNGs they came from, which matters for screenshots full of small text.
• Thumbnail is 300x300 WebP as the contribution guide requires; the manufacturer logo is new.
• Built locally with npm run build before submitting: the page and all eleven images render, and the
  Astrolabs card appears on the Focusers, Dust Caps, Light Boxes and Auxiliaries listings.