docs: Add information about systemd timers in README

README.md

@@ -2,16 +2,49 @@
 This repo will allow one to build [ReVanced](https://github.com/revanced/) apps automatically and post it to a telegram channel to access and possibly share the builds with friends. It uses [Gotify](https://gotify.net), [ntfy.sh](https://ntfy.sh) or [telegram.sh](https://github.com/fabianonline/telegram.sh) to send messages and [telegram-upload](https://github.com/Nekmo/telegram-upload) to upload files (optionally, disabled out by default). Make sure that `Java >=17` is installed and selected as default.
 
 ## How to use
-Just run `./build_revanced <working-directory> (force/clean/experimental/checkonly/buildonly)`. Might be a good idea to set it up to run periodically using cron. I currently use the following in a user crontab to run it everyday at 6 AM:
-```
-0 6 * * * <full-script-location> <full-working-directory-location>
-```
+Just run `./build_revanced <working-directory> (force/clean/experimental/checkonly/buildonly)`. Might be a good idea to set it up to run periodically. There are a few ways of doing it.
+1. Just drop it inside `/etc/cron.daily/`.
+1. To make it run at a specific time (6AM in the example) using `cron`, put this in your `crontab`:
+    ```crontab
+    0 6 * * * <full-script-location> <full-working-directory-location>
+    ```
+1. The exact same thing as in 2 can be achieved using `systemd` timers instead. Create the following files.
+    ```toml
+    /etc/systemd/system/revanced-builder.service
+    ---------------------------------------------
+    [Unit]
+    Description=Automatically build new builds of ReVanced
+    Wants=network-online.target
+    After=network-online.target
+
+    [Service]
+    Type=oneshot
+    User=<user>
+    Group=<group>
+    ExecStart=_JAVA_OPTIONS='-Xmx512m' <full-script-location> <full-working-directory-location>
+    ```
+    ```toml
+    /etc/systemd/system/revanced-builder.timer
+    -------------------------------------------
+    [Unit]
+    Description=Automatically build new builds of ReVanced
+
+    [Timer]
+    OnCalendar=*-*-* 6:00:00
+
+    [Install]
+    WantedBy=timers.target
+    ```
+    and then enable the timer using
+    ```bash
+    sudo systemctl enable --now revanced-builder.timer
+    ```
 
 ## Notes
 - The following programs are needed to run this script. Make sure that you have them in your `$PATH`.
- ```
- htmlq jq wget java curl
- ```
+    ```
+    htmlq jq wget java curl
+    ```
 - To enable build for a particular apk, copy the `build_settings` file to your working directory and modify it to suit your needs.
 - The script will download the **automatically selected compatible version** (using compatibility of patches as listed [here](https://github.com/revanced/revanced-patches#list-of-available-patches)) of Youtube on APKPure, **NOT** latest official version on Google Play.
 - Under **NO CIRCUMSTANCES** any APKs will be uploaded to this repository to avoid DMCA.