fix #173 cloudmergin to merginmaps.com

[alex-cit]

fix #173 replaced main platform name in text and also in vuepress components. Please check if I did that correctly. The component refers to merginmaps.com, although there was an instance (https://merginmaps.com/docs/setup/sign-up-to-mergin-maps/#forgotten-password) which would need "app.merginmaps.com". In other cases, it seems to me to better link the main page (merginmaps.com) rather than the login page (app.merginmaps.com). There are still 2 references to cloudmergin.com:

• https://merginmaps.com/docs/layer/plugin-variables/ - I tried this in QGIS and the variable '@mergin_url' still refers to https://public.cloudmergin.com in QGIS, so I did not change it in this docs yet
• https://merginmaps.com/docs/dev/integration/ is maybe a similar case: " --url Mergin url (defaults to public.cloudmergin.com)". This is still valid?

[PeterPetrik]

public.cloudmergin.com is proxied to app.merginmaps.com so you can have the new URL in docs without problem

I would change both of these, we will release it soon

• mergin_url: see https://github.com/lutraconsulting/qgis-mergin-plugin/issues/414
• re integration: see https://github.com/lutraconsulting/mergin-py-client/pull/137

[alex-cit]

added new component AppDomainLinkName

• added components to https://merginmaps.com/docs/misc/write-docs/
• replaced inputapp.io links
• used components instead of plain text when possible (e.g. Input)