feat: XDG taskrc config (#2380)

Co-authored-by: Valentin Maerten <maerten.valentin@gmail.com>

website/src/docs/reference/config.md

@@ -0,0 +1,70 @@
+---
+title: Configuration Reference
+description: Complete reference for the Task config files and env vars
+permalink: /reference/config/
+outline: deep
+---
+
+# Configuration Reference
+
+Task has multiple ways of being configured. These methods are parsed, in
+sequence, in the following order with the highest priority last:
+
+- [Environment variables](./environment.md)
+- _Configuration files_
+- [Command-line flags](./cli.md)
+
+In this document, we will look at the second of the three options, configuration
+files.
+
+## File Precedence
+
+Task's configuration files are named `.taskrc.yml` or `.taskrc.yaml`. Task will
+automatically look for directories containing files with these names in the
+following order with the highest priority first:
+
+- Current directory (or the one specified by the `--taskfile`/`--entrypoint`
+  flags).
+- Each directory walking up the file tree from the current directory (or the one
+  specified by the `--taskfile`/`--entrypoint` flags) until we reach the user's
+  home directory or the root directory of that drive.
+- `$XDG_CONFIG_HOME/task`.
+
+All config files will be merged together into a unified config, starting with
+the lowest priority file in `$XDG_CONFIG_HOME/task` with each subsequent file
+overwriting the previous one if values are set.
+
+For example, given the following files:
+
+```yaml [$XDG_CONFIG_HOME/task/.taskrc.yml]
+# lowest priority global config
+option_1: foo
+option_2: foo
+option_3: foo
+```
+
+```yaml [$HOME/.taskrc.yml]
+option_1: bar
+option_2: bar
+```
+
+```yaml [$HOME/path/to/project/.taskrc.yml]
+# highest priority project config
+option_1: baz
+```
+
+You would end up with the following configuration:
+
+```yaml
+option_1: baz # Taken from $HOME/path/to/project/.taskrc.yml
+option_2: bar # Taken from $HOME/.taskrc.yml
+option_3: foo # Taken from $XDG_CONFIG_HOME/task/.taskrc.yml
+```
+
+## Configuration Options
+
+### `experiments`
+
+The experiments section allows you to enable Task's experimental features. These
+options are not enumerated here. Instead, please refer to our
+[experiments documentation](../experiments/index.md) for more information.