Add links to tile provider authentication docs (#914)

This probably confused some people in the past, since vector tiles won't
even display an access denied image ;)

Before (no information on access keys and where to get them):

<img width="411" alt="image"
src="https://github.com/user-attachments/assets/8820fb20-bda4-460c-9cc9-8fec5daa480d">

After (add links to providers in info callout + add a field for Stadia
Maps API keys):

<img width="395" alt="image"
src="https://github.com/user-attachments/assets/91ee732c-b3f5-45f8-81a6-8d896a93f644">

---------

Co-authored-by: Harel M <harel.mazor@gmail.com>
Co-authored-by: Joscha <34318751+josxha@users.noreply.github.com>
Co-authored-by: Hugues Tavernier <hugues.tavernier@protonmail.com>
Co-authored-by: Keitaroh Kobayashi <keita@kbys.me>

src/components/ModalSettings.tsx

@@ -156,6 +156,14 @@ class ModalSettingsInternal extends React.Component<ModalSettingsInternalProps>
           onChange={onChangeMetadataProperty.bind(this, "maputnik:thunderforest_access_token")}
         />
 
+        <FieldString
+          label={fsa.maputnik.stadia_access_token.label}
+          fieldSpec={fsa.maputnik.stadia_access_token}
+          data-wd-key="modal:settings.maputnik:stadia_access_token"
+          value={metadata['maputnik:stadia_access_token']}
+          onChange={onChangeMetadataProperty.bind(this, "maputnik:stadia_access_token")}
+        />
+
         <FieldArray
           label={t("Center")}
           fieldSpec={latest.$root.center}