feat: setup monorepo using pnpm (#20)

* tests: fix float problems and PAT problem

* extend CONTRIBUTING.md

* extend build documentation, add GH action, fix build on MacOS

* fix build on Vercel

* update .gitignore and CONTRIBUTING.md

* feat: begin work on monorepo

* chore(actions/basic-build): use pnpm

* fix: vercel-deploy

* docs: updates with new folders

* chore: apply PR review comments

---------

Co-authored-by: martin-mfg <2026226+martin-mfg@users.noreply.github.com>

.github/CONTRIBUTING.md

@@ -2,12 +2,15 @@
 
 ## Local Development
 
-To run and test GitHub-Stats-Extended, you need to follow a few simple steps:
+To set up the project GitHub-Stats-Extended locally, run the following commands:
 
-1. create [your own deployment](../docs/deploy.md)
-2. optional: add an SQL database; by using e.g. the ["Nile" integration](https://vercel.com/marketplace/nile) or by manually setting the environment variable `POSTGRES_URL`
-3. optional: [create your own OAuth App](https://github.com/settings/developers) and set environment variables `OAUTH_REDIRECT_URI`, `OAUTH_CLIENT_ID` and `OAUTH_CLIENT_SECRET` on Vercel accordingly
-4. optional: in addition to the Vercel project based on the `backend` folder, create a second project based on the `frontend/frontend` folder. No environment variables needed.
+```bash
+./vercel-preparation.sh
+pnpm install
+pnpm --filter frontend run build-trends
+```
+
+The easiest way to run and test the project is to deploy it to Vercel as described in the [deployment guide](../docs/deploy.md).
 
 ## Themes Contribution
 
@@ -37,9 +40,9 @@ We use GitHub issues to track public bugs. Report a bug by [opening a new issue]
 
 > **Ans:** Please read all the related issues/comments before opening any issues regarding language card stats:
 >
-> -   <https://github.com/anuraghazra/github-readme-stats/issues/136#issuecomment-665164174>
+> - <https://github.com/anuraghazra/github-readme-stats/issues/136#issuecomment-665164174>
 >
-> -   <https://github.com/anuraghazra/github-readme-stats/issues/136#issuecomment-665172181>
+> - <https://github.com/anuraghazra/github-readme-stats/issues/136#issuecomment-665172181>
 
 **Q:** How to count private stats?
 
@@ -49,6 +52,6 @@ We use GitHub issues to track public bugs. Report a bug by [opening a new issue]
 
 **Great Feature Requests** tend to have:
 
--   A quick idea summary
--   What & why do you want to add the specific feature
--   Additional context like images, links to resources to implement the feature, etc.
+- A quick idea summary
+- What & why do you want to add the specific feature
+- Additional context like images, links to resources to implement the feature, etc.

.github/actions/install-dependencies/action.yml

@@ -0,0 +1,37 @@
+name: Setup Node.js + PNPM and install Dependencies
+description: |
+  This is a composite GitHub Action that:
+  - Sets up pnpm package manager
+  - Configures Node.js environment
+  - Installs project dependencies with caching
+
+inputs:
+  node-version:
+    description: "Explicit node version. Otherwise fallback reading `.nvmrc`"
+
+runs:
+  using: composite
+
+  steps:
+    - name: Install pnpm
+      uses: pnpm/action-setup@v4
+
+    - name: Setup Node.js (via input)
+      if: ${{ inputs.node-version }}
+      uses: actions/setup-node@v6
+      with:
+        node-version: ${{ inputs.node-version }}
+        cache: "pnpm"
+        registry-url: "https://registry.npmjs.org"
+
+    - name: Setup Node.js (via .nvmrc)
+      if: ${{ !inputs.node-version }}
+      uses: actions/setup-node@v6
+      with:
+        node-version-file: ".nvmrc"
+        cache: "pnpm"
+        registry-url: "https://registry.npmjs.org"
+
+    - name: Install Dependencies
+      shell: bash
+      run: pnpm install --frozen-lockfile

.github/workflows/basic-build.yml

@@ -0,0 +1,31 @@
+name: Basic Build
+
+on:
+  workflow_dispatch: # Allows you to run this manually from the Actions tab
+  push:
+  pull_request:
+
+jobs:
+  build-and-test:
+    name: Build and test on ${{ matrix.os }}
+
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+
+      - name: Install Dependencies
+        uses: ./.github/actions/install-dependencies
+
+      - name: Run vercel-preparation.sh
+        run: |
+          chmod +x ./vercel-preparation.sh
+          ./vercel-preparation.sh
+
+      - name: Build frontend
+        run: pnpm --filter frontend run build-trends