Enter prerelease mode (#2578)

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- [x] I wrote a PR title in **English** and added an appropriate
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- [x] I [added the
**changeset**](https://github.com/changesets/changesets/blob/main/docs/adding-a-changeset.md)
about the changes that needed to be released. (or didn't have to)
- [x] I wrote or updated **documentation** related to the changes. (or
didn't have to)
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  - Windows: Chrome, Edge, (Optional) Firefox
  - macOS: Chrome, Edge, Safari, (Optional) Firefox

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<!-- Fixes #0000 -->

<!-- Please brief explanation of the changes made -->

컬러 토큰 마이그레이션을 위해 프리릴리즈 모드로 진입합니다.

<!-- Please elaborate description of the changes -->

- main 브랜치 헤드 커밋 기준으로 alpha 브랜치를 생성
- changeset prerelease mode 진입
- CI 브랜치 필터에 alpha 브랜치 필터 추가

이 PR 이후 bezier-react의 기존 컴포넌트들에서 alpha 컬러 토큰 지원 작업을 진행할 예정입니다.

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No

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Author: sungik-choi

.changeset/pre.json

@@ -0,0 +1,16 @@
+{
+  "mode": "pre",
+  "tag": "alpha",
+  "initialVersions": {
+    "eslint-config-bezier": "0.0.1",
+    "tsconfig": "0.0.1",
+    "@channel.io/bezier-codemod": "0.5.0",
+    "bezier-figma-plugin": "0.6.23",
+    "@channel.io/bezier-icons": "0.39.0",
+    "@channel.io/bezier-react": "3.0.3",
+    "@channel.io/bezier-tokens": "0.3.0",
+    "bezier-vscode": "0.4.0",
+    "@channel.io/stylelint-bezier": "0.2.8"
+  },
+  "changesets": []
+}

.github/workflows/chromatic.yml

@@ -4,6 +4,7 @@ on:
   push:
     branches:
       - main
+      - alpha
   pull_request:
     paths:
       - packages/bezier-react/**

.github/workflows/ci.yml

@@ -3,6 +3,7 @@ on:
   push:
     branches:
       - main
+      - alpha
   pull_request:
 
 jobs:

.github/workflows/code-connect.yml

@@ -6,6 +6,7 @@ on:
       - packages/bezier-react/src/components/**/*.figma.tsx
     branches:
       - main
+      - alpha
 
 jobs:
   code-connect: