docs: improve overall documentation

.github/readme/partials/documentation/setup/web.md

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+# 🏗️ Deploying your own web instance (~20 min setup, depending on your sysadmin knowledge)
+
+Setup a metrics instance on your server if you don't want to use GitHub Actions and [metrics.lecoq.io](https://metrics.lecoq.io).
+See all supported options in [settings.example.json](/settings.example.json).
+
+Assuming your username is `my-github-user`, you can then embed rendered metrics in your readme like below:
+
+```markdown
+![Metrics](https://my-personal-domain.com/my-github-user)
+```
+
+## 💬 How to setup?
+
+### 0. Prepare your server
+
+You'll need a server with a recent version of [Docker](https://www.docker.com/).
+
+### 1. Create a GitHub personal token
+
+From the `Developer settings` of your account settings, select `Personal access tokens` to create a new token.
+
+No additional scopes are needed.
+
+![Setup a GitHub personal token](/.github/readme/imgs/setup_personal_token.png)
+
+### 2. Configure your instance
+
+Fetch [settings.example.json](/settings.example.json) which contains all supported option.
+```shell
+wget https://raw.githubusercontent.com/lowlighter/metrics/master/settings.example.json
+```
+
+Edit `settings.json` to configure your instance.
+
+```javascript
+{
+  //GitHub API token
+    "token":"GITHUB_TOKEN",
+  //Other options...
+}
+```
+
+If you plan to make your web instance public, it is advised to restrict its access thanks to rate limiter and access list.
+
+### 3. Start docker container
+
+Metrics docker images are published on [GitHub Container Registry](https://github.com/lowlighter/metrics/pkgs/container/metrics).
+
+Configure the following variables (or hardcode them in the command in the next block):
+```shell
+# Select an existing docker image tag
+VERSION=latest
+# Path to configured `settings.json`
+SETTINGS=/path/to/settings.json
+# Port used internally (use the same one than in `settings.json`)
+SERVICE_PORT=3000
+# Port to publish
+PUBLISHED_PORT=80
+```
+
+And start the container using the following command:
+```shell
+docker run -d --workdir=/metrics --entrypoint="" -p=127.0.0.1:$PUBLISHED_PORT:$SERVICE_PORT --volume=$SETTINGS:/metrics/settings.json ghcr.io/lowlighter/metrics:$VERSION npm start
+```
+
+### 4. Embed link into your README.md
+
+Edit your repository readme and add your metrics image from your server domain:
+
+```markdown
+![Metrics](https://my-personal-domain.com/my-github-user)
+```
+
+### 5. (optional) Setup your instance as a service
+
+To ensure that your instance will restart if it reboots or crashes, you should set it up as a service.
+This is described below for Linux-like systems which support *systemd*.
+
+Create a new service file `/etc/systemd/system/github_metrics.service` and paste the following after editing paths inside:
+
+```ini
+[Unit]
+Description=Metrics
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+ExecStart=(command to run as service)
+
+[Install]
+WantedBy=multi-user.target
+```
+
+Reload services, enable it, start it and check if it is up and running:
+
+```shell
+systemctl daemon-reload
+systemctl enable github_metrics
+systemctl start github_metrics
+systemctl status github_metrics
+```
+
+### Alternative option: run an instance locally (intended for testing and development)
+
+To run an instance without docker, you'll need to have [NodeJS](https://nodejs.org) (see used version in [Dockerfile](/Dockerfile#L1-L2)) installed.
+
+Clone repository, install dependencies and copy configuration example to `settings.json`:
+
+```shell
+git clone https://github.com/lowlighter/metrics.git
+cd metrics/
+npm install --only=prod
+cp settings.example.json settings.json
+```
+
+Once you've finished configuring metrics, start your instance using the following command:
+
+```shell
+npm start
+```
+
+You should now be able to access your server with provided port in `setting.json` from your browser.
+
+## 🔗 HTTP parameters
+
+Most of options from [action.yml](/action.yml) are actually supported by web instance, though syntax is slightly different.
+All underscores (`_`) must be replaced by dots (`.`) and `plugin_` prefixes must be dropped.
+
+For example, to configure pagespeed plugin you'd use the following:
+```
+https://my-personal-domain.com/my-github-user?pagespeed=1&pagespeed.detailed=1&pagespeed.url=https%3A%2F%2Fexample.com
+```
+
+Note that url parameters must be [encoded](https://developer.mozilla.org/fr/docs/Web/JavaScript/Reference/Objets_globaux/encodeURIComponent).
+
+As for `base` content, which is enabled by default, sections are available through "`base.<section>`".
+
+For example, to display only `repositories` section, use:
+```
+https://my-personal-domain.com/my-github-user?base=0&base.repositories=1
+```