Even more flag flair (#959)

## Description:

Add Sakhalin flag for nation on Japan map. Use Aztec flag for Biggest
Snakes nation. Change 'Jesuit Monks' nation into 'Tamazgha' with
corresponding flag. Thanks @ N0ur and J. Dimlight

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

## Please put your Discord username so you can be contacted if a bug or
regression is found:

tryout33

resources/maps/GatewayToTheAtlantic.json

@@ -119,9 +119,9 @@
     },
     {
       "coordinates": [2097, 1670],
-      "name": "Jesuit Monks",
+      "name": "Tamazgha",
       "strength": 2,
-      "flag": ""
+      "flag": "Amazigh flag"
     },
     {
       "coordinates": [979, 1013],

resources/maps/Japan.json

@@ -31,7 +31,7 @@
       "coordinates": [1162, 154],
       "name": "Sakhalin",
       "strength": 2,
-      "flag": ""
+      "flag": "Sakhalin"
     },
     {
       "coordinates": [571, 1116],

resources/maps/SouthAmerica.json

@@ -133,7 +133,7 @@
       "coordinates": [1270, 1035],
       "name": "The Biggest Snakes",
       "strength": 3,
-      "flag": ""
+      "flag": "Aztec Empire"
     },
     {
       "coordinates": [894, 693],