[matter] Fix image links

[jlaur]

This is an attempt to fix images in the Matter documentation.

There are four image files: https://github.com/openhab/openhab-addons/tree/main/bundles/org.openhab.binding.matter/doc

These images work:

• <img src="./doc/bridge-settings.png" alt="Bridge Settings" width="500"/> becomes <img src="/assets/img/bridge-settings.e0306381.png" alt="Bridge Settings" width="500">
• <img src="./doc/bridge-settings-pair.png" alt="Commissioning Window" width="500"/> becomes <img src="/assets/img/bridge-settings-pair.d4048767.png" alt="Commissioning Window" width="500">

And these do not:

• <img src="doc/thing-discovery.png" alt="Thing Discovery" width="600"/> becomes <img src="doc/thing-discovery.png" alt="Thing Discovery" width="600">
• <img src="doc/pairing.png" alt="Matter Pairing" width="600"/> becomes <img src="doc/pairing.png" alt="Matter Pairing" width="600">

The only difference seems to be the current directory reference in two of them: ./. Those two happens to be working, but I'm not sure that's the reason. Could it be that they all need to be either with or without? For example, the MyBMW binding doesn't use ./ and all images seem to work.

It could also be a completely different issue that I have missed. In any case, it probably won't hurt to make these links consistent.

[jlaur]

@stefan-hoehn - maybe you have something to add here?

[digitaldan]

LGTM, thanks!

[lsiepel]

Thanks, LGTM

[jlaur]

This PR didn't break the images that already worked, but unfortunately it didn't fix those that don't work either.

EDIT: Sorry, there hasn't been a build yet, so will have to check again: https://ci.openhab.org/view/Documentation/