Adds provider name to fix welcomepage text.

* Removes unused ADD_PEOPLE_APP_NAME
* Moves deep-link header background and logo size as variables.
* Fixes more numbers page space in the header.
* Fixes left padding on deep-linking mobile page.

css/_variables.scss

 $welcomePageFontFamily: inherit;
 $welcomePageHeaderBackground: linear-gradient(-90deg, #1251AE 0%, #0074FF 50%, #1251AE 100%);
 $welcomePageTitleColor: #fff;
+
+/**
+ * Deep-linking page variables.
+ */
+$deepLinkingMobileLogoHeight: 40px;
+$deepLinkingMobileHeaderBackground: #f1f2f5;

css/deep-linking/_mobile.scss

     .header {
         width: 100%;
         height: 70px;
-        background-color: #f1f2f5;
+        background-color: $deepLinkingMobileHeaderBackground;
         text-align: center;
         .logo {
             margin-top: 15px;
             margin-left: auto;
             margin-right: auto;
-            height: 40px;
+            height: $deepLinkingMobileLogoHeight;
         }
     }
 
 
         .dial-in-numbers-list {
             color: $unsupportedBrowserTextColor;
+            padding-left: 20px;
         }
 
         .dial-in-numbers-body {

css/modals/invite/_info.scss

     .dial-in-conference-id {
         text-align: center;
         min-width: 200px;
+        margin-top: 40px;
     }
 
     .dial-in-conference-name,

doc/sipgw-config.md

   peopleSearchQueryTypes: ['conferenceRooms'],
   peopleSearchUrl: 'https://api.yourdomain.com/testpath/searchpeople',
 ```
- - interface_config.js:
-```
-  ADD_PEOPLE_APP_NAME: 'Jitsi'
-```
 
 The combination of the above settings and providing a jwt token will enable a button under invite option which will show the dialog 'Add people'.
 

interface_config.js

     DISPLAY_WELCOME_PAGE_CONTENT: true,
     APP_NAME: 'Jitsi Meet',
     NATIVE_APP_NAME: 'Jitsi Meet',
+    PROVIDER_NAME: 'Jitsi',
     LANG_DETECTION: false, // Allow i18n to detect the system language
     INVITATION_POWERED_BY: true,
 
      */
     CONNECTION_INDICATOR_DISABLED: false,
 
-    /**
-     * The name of the application connected to the "Add people" search service.
-     */
-    // ADD_PEOPLE_APP_NAME: "",
-
     /**
      * If true, hides the video quality label indicating the resolution status
      * of the current large video.

lang/main.json

         },
         "calendar": "Calendar",
         "connectCalendarButton": "Connect your calendar",
-        "connectCalendarText": "Connect your calendar to view all your meetings in __app__. Plus, add __app__ meetings to your calendar and start them with one click.",
+        "connectCalendarText": "Connect your calendar to view all your meetings in __app__. Plus, add __provider__ meetings to your calendar and start them with one click.",
         "enterRoomTitle": "Start a new meeting",
         "go": "GO",
         "join": "JOIN",

react/features/calendar-sync/components/CalendarList.web.js

             <div className = 'meetings-list-empty'>
                 <p className = 'description'>
                     { t('welcomepage.connectCalendarText', {
-                        app: interfaceConfig.APP_NAME
+                        app: interfaceConfig.APP_NAME,
+                        provider: interfaceConfig.PROVIDER_NAME
                     }) }
                 </p>
                 <div