Add simple docs for userdev (#193)

* Add simple docs for userdev

* more work on userdev docs

* consistent casing

* do last suggestion

* address final comments

Author: Machine-Maker

config/sidebar.paper.ts

@@ -84,6 +84,7 @@ const paper: SidebarsConfig = {
           },
           items: [
             "dev/getting-started/project-setup",
+            "dev/getting-started/userdev",
             "dev/getting-started/plugin-yml",
             "dev/getting-started/paper-plugins",
           ],

docs/paper/dev/getting-started/userdev.md

@@ -0,0 +1,97 @@
+---
+slug: /dev/userdev
+sidebar_label: Paperweight Userdev
+---
+
+# paperweight-userdev
+
+**paperweight** is the name of Paper's custom build tooling. The **paperweight-userdev** Gradle plugin part of that
+provides access to internal code (also known as NMS) during development.
+
+:::note
+
+This guide is written using the Kotlin DSL for Gradle and assumes you have some basic knowledge of Gradle.
+If you want to see a fully-functioning plugin that uses **paperweight-userdev**,
+check out this [example plugin](https://github.com/PaperMC/paperweight-test-plugin).
+
+:::
+
+## Why this is useful
+The Paper server jars we provide on the downloads page through the API are **paperclip** jars. These
+use Spigot's mappings, which are essentially some type names, but fully obfuscated fields and methods.
+This can make it hard to work with in a development environment. This plugin lets you use fully deobfuscated
+types, names and fields during development, and then remaps your plugin, so it can still be used with the obfuscated
+server.
+
+:::caution
+
+The re-obfuscation does not apply to reflection. Look at something like [this library](https://github.com/jpenilla/reflection-remapper) to be able to
+use non-obfuscated names in reflection.
+
+:::
+
+## Adding the plugin
+Add the plugin to your `build.gradle.kts` file.
+```kotlin
+plugins {
+    id("io.papermc.paperweight.userdev") version "1.5.5" // the latest version can be found on the Gradle Plugin Portal
+}
+```
+
+:::info[Snapshots]
+
+**paperweight-userdev** releases are available through the Gradle plugin portal, but if you
+want to use SNAPSHOT versions, you must add Paper's maven repo to `settings.gradle.kts` with:
+```kotlin
+pluginManagement {
+    repositores {
+        maven("https://repo.papermc.io/repository/maven-public/")
+    }
+}
+```
+
+:::
+
+## Adding the dev-bundle dependency
+If you try to load your Gradle project now, you will receive an error saying you have to declare
+a dev bundle dependency. You can do that by adding to your `dependencies` block in your `build.gradle.kts`
+file.
+
+```kotlin
+dependencies {
+    // Other Dependencies
+    paperweight.paperDevBundle("1.20.1-R0.1-SNAPSHOT")
+}
+```
+:::tip
+
+You can remove any dependency for the Paper API, as the dev bundle includes that.
+
+:::
+
+## Gradle Tasks
+
+### reobfJar
+
+This task creates a plugin jar that is re-obfuscated to Spigot's runtime mappings.
+This means it will work on standard Paper servers.
+
+The output will be inside the `build/libs` folder. The jar whose filename includes `-dev`
+is mojang-mapped (not re-obfuscated) and will not work on most servers.
+
+:::info[Shadow]
+
+If you have the shadow Gradle plugin applied in your build script, **paperweight-userdev** will
+detect that and use the shaded jar as the input for the `reobfJar` task.
+
+The `-dev-all.jar` file in `build/libs` is the shaded, but not re-obfuscated jar.
+
+:::
+
+You can make the `reobfJar` task run on the default `build` task with:
+```kotlin
+tasks.assemble {
+    dependsOn(reobfJar)
+}
+```
+