feat: drop Unity 2021 support (#1288)

Author: homuler

.github/workflows/linux-test.yml

@@ -118,7 +118,6 @@ jobs:
           - ubuntu-22.04
         unityVersion:
           - 2022.3.34f1
-          - 2021.3.33f1
     steps:
       - name: Install UnityEditor
         run: |

.github/workflows/macos-test.yml

@@ -96,7 +96,6 @@ jobs:
           - macos-13
         unity:
           - { version: "2022.3.34f1", changeset: "4886f5360533" }
-          - { version: "2021.3.33f1", changeset: "ee5a2aa03ab2" }
     steps:
       - name: Install UnityEditor
         run: |

.github/workflows/windows-test.yml

@@ -93,7 +93,6 @@ jobs:
           - windows-2019
         unity:
           - { version: "2022.3.34f1", changeset: "4886f5360533" }
-          - { version: "2021.3.33f1", changeset: "ee5a2aa03ab2" }
     steps:
       - name: Install UnityHub
         uses: crazy-max/ghaction-chocolatey@v3

Packages/com.github.homuler.mediapipe/package.json

@@ -3,7 +3,7 @@
   "version": "0.15.0",
   "displayName": "MediaPipe Unity Plugin",
   "description": "A Unity Plugin to run MediaPipe CalculatorGraph",
-  "unity": "2021.3",
+  "unity": "2022.3",
   "author": {
     "name": "homuler"
   },

README.md

@@ -1,6 +1,6 @@
 # MediaPipe Unity Plugin
 
-This is a Unity (>= 2021.3) [Native Plugin](https://docs.unity3d.com/Manual/NativePlugins.html) to use [MediaPipe](https://github.com/google/mediapipe) (0.10.14).
+This is a Unity (>= 2022.3) [Native Plugin](https://docs.unity3d.com/Manual/NativePlugins.html) to use [MediaPipe](https://github.com/google/mediapipe) (0.10.14).
 
 The goal of this project is to port the MediaPipe API (C++) _one by one_ to C# so that it can be called from Unity.\
 This approach may sacrifice performance when you need to call multiple APIs in a loop, but it gives you the flexibility to use MediaPipe instead.