chore: implement PR to linear issues linker

linear/link-pr-to-linear-issue/README.md

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+### Overview
+
+This is a github action to link a GitHub PR to Linear issues, because Linear doesn't do that automatically. It supports all the GitHub magic words (closes, fixes, etc.) so that when a PR closes an issue via magic words, the action finds the Linear issues related to the closing issues and links them by adding a comment in the PR's body with Linear magic words that close that Linear issue:
+
+```md
+<!-- LINEAR: closes LIN-ID-1, LIN-ID-2 -->
+
+- Closes #ISSUE1,
+- Closes #ISSUE2
+```
+
+If one wants to relate a PR to an issue without setting it as closing for that issue, they can add a "relates to", "related to", or "part of".
+This adds a markdown comment which relates the PR to linear issues without tagging the PR as closing in Linear:
+
+```md
+<!-- LINEAR: relates to LIN-ID-1, LIN-ID-2, LIN-ID-3 -->
+
+- Relates to #ISSUE1
+- Related to #ISSUE2
+- Part of #ISSUE3
+```
+
+Besides linking issues, the action also unlinks issues from PRs for cases where somebody erroneously links the wrong issue in GitHub (e.g. wanted to close #ISSUE2 but wrote that it closes #ISSUE1 and then they edit it to the correct issue). This isn't automatically handled by Linear when the related Linear issue's identifier is removed from the body of the PR.
+
+### How to use?
+
+```yml
+- uses: FuelLabs/github-actions/linear/link-pr-to-linear-issue@master
+  with:
+    repository: ${{ github.repository }} # You can omit it 
+    pull_number: ${{ github.event.client_payload.ref }}  
+    linear_api_key: ${{ secrets.LINEAR_TOKEN }}
+    github_token: ${{ secrets.REPO_TOKEN }}
+```
+
+### Inputs
+
+| Name           | Description                                                | Default                    |
+| -------------- | ---------------------------------------------------------- | -------------------------- |
+| repository     | Github Repository                                          | `${{ github.repository }}` |
+| pull_number    | The PR number who's body will be read and updated          |                            |
+| linear_api_key | Linear API key to use                                      |                            |
+| github_token   | A token with write permissions for updating the PR body    |                            |
+
+
+## License
+
+The primary license for this repo is `Apache 2.0`, see [`LICENSE`](../LICENSE.md).

linear/link-pr-to-linear-issue/action.yaml

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+name: "Link PR to Linear Issues"
+description: "Workflow for linking PRs to Linear issues"
+
+inputs:
+  repository:
+    description: "Github Repository"
+    default: ${{ github.repository }}
+  pull_number:
+    description: "PR number to link to linear issues"
+    default: ${{ github.event.client_payload.ref }} 
+    required: true
+  linear_api_key:
+    description: "Linear API key"
+    required: true
+  github_token:
+    description: "Github token"
+    required: true
+
+runs:
+  using: "node20"
+  main: "dist/index.js"

linear/link-pr-to-linear-issue/package.json

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+{
+  "name": "link-pr-to-linear-issue",
+  "version": "1.0.0",
+  "description": "",
+  "main": "./src/index.ts",
+  "scripts": {
+    "test": "vitest run --config vitest.config.ts",
+    "prebuild": "pnpm test",
+    "build": "tsup"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "dependencies": {
+    "@actions/core": "^1.10.1",
+    "@actions/github": "^6.0.0",
+    "@linear/sdk": "^30.0.0"
+  },
+  "devDependencies": {
+    "@fuels/ts-config": "^0.20.0",
+    "@types/node": "^22.6.1",
+    "tsup": "^8.3.0",
+    "vitest": "^2.1.1"
+  }
+}