fabric-*: require Fabric Loader 0.12.12

This is the release that includes all current log4j mitigation.
Changes in fabric.mod.json ensure the mod will completely refuse to load
unless it's on a fully patched Fabric server.

fabric-1.15.2/gradle.properties

@@ -4,9 +4,9 @@ org.gradle.jvmargs=-Xmx1G
 # check these on https://fabricmc.net/use
 minecraft_version=1.15.2
 yarn_mappings=1.15.2+build.17
-loader_version=0.10.1+build.209
+loader_version=0.12.12
 # Mod Properties
 archives_base_name=Dynmap
 # Dependencies
 # currently not on the main fabric site, check on the maven: https://maven.fabricmc.net/net/fabricmc/fabric-api/fabric-api
-fabric_version=0.23.0+build.328-1.15
+fabric_version=0.23.0+build.328-1.15

fabric-1.15.2/src/main/resources/fabric.mod.json

@@ -26,7 +26,7 @@
   ],
 
   "depends": {
-    "fabricloader": ">=0.7.4",
+    "fabricloader": ">=0.12.12",
     "fabric": ">=0.17.0",
     "minecraft": "1.15.2"
   }