Created simple contributing

CONTRIBUTING.md

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+# Contributing to Mojang Maps
+
+Contributing to Mojang Maps is easy!
+
+## Some standards
+
+Everything has to be compatible with Java 8/Minecraft 1.16.5. You can check this by running
+`./gradlew build -PmcVer=1.16.5`.
+Replace `./gradlew` with `.\gradlew` or just `gradlew`.
+
+Here are some replacements of common functions:
+
+```java
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Random;
+
+public class Replacements() {
+
+    private Random random = new Random();
+
+    public void replacements() {
+
+        // Instead of
+        List.of();
+        // Use
+        Arrays.asList();
+        // or
+        Collections.singletonList();
+
+        // Instead of
+        Path.of();
+        // Use
+        Paths.get();
+
+        // Instead of
+        """
+                Message block
+                Cool
+                """;
+        // Use
+        "Message block\n" +
+                "Cool\n";
+
+        // Don't know if this is a Java 8 thing, but it didn't work on 1.16.5
+        // Instead of
+        int number = random.nextInt(256);
+        // Use
+        int number = random.nextInt() * 256;
+
+    }
+
+}
+```
+
+Instead of using a record, please write it as a fully written class.
+
+## Writing to the pathfinding project
+
+Because pathfinding is based on another project, it uses patches.
+
+### Setup
+
+To set up the project, run
+`./gradlew applyPatches`
+If you get any errors, run `./gradlew updateSubmodules` beforehand.
+
+### Making a new patch
+
+Make a commit in the pathfinding folder. The name should be the name of the commit. Then run (in the root folder)
+`./gradlew makePatches`.
+
+### Editing a new patch
+
+I'm to lazy to write this. Go
+to [this part (Method 1) of Papers CONTRIBUTING.MD](https://github.com/PaperMC/Paper/blob/93b435dbab92d071bd685c6d8dda9fd32c4c2990/CONTRIBUTING.md#method-1)
+and follow the steps in the pathfinding.
+
+Instead of using `git rebase -i base`, use `git rebase -i upstream`. And instead of using `./gradlew rebuildPatches`,
+use `./gradlew makePatches`.
+Instead of using `git rebase -i base`, use `git rebase -i upstream`. And instead of using `./gradlew rebuildPatches`,
+use `./gradlew makePatches`.
+
+## Building
+
+Because the pathfinding api uses patches, please set up the pathfinding project. Please follow the setup instructions
+for pathfinding.
+
+After that, run `./gradlew build`