Add readme file to give at least some infos

README.md

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+# Webhookey
+
+## Build
+
+### Install Rust
+The Rust toolchain needs to be installed:
+``` sh
+    curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
+```
+
+Further, for Rocket we need to have the nightly toolchain installed:
+``` sh
+    rustup toolchain install nightly
+```
+
+### Build Webhookey
+The webhookey project can be built for development:
+``` sh
+    cargo b
+```
+
+or for releasing:
+``` sh
+    cargo b --release
+```
+
+### Install Webhookey
+When a Rust toolchain installed you can also install Webhookey
+directly without cloning it manualy:
+``` sh
+    cargo install --git https://git.onders.org/finga/webhookey.git webhookey
+```
+
+or from within the project:
+``` sh
+    cargo install webhookey
+```
+
+### Run Webhookey
+Webhookey can either be run from the project directory with:
+``` sh
+    cargo b
+```
+
+or you can copy the produced binary somewhere else from
+`webhookey/target/{debug, release}/webhookey` depending on which one
+you built.
+
+## Configuration
+Configuration syntax is YAML and has to be done in following order:
+
+Right now there is only the configuration parameter for hooks, here
+each hook has to be configured, It contains following fields:
+- action: optional string for the action to be executed when all
+  filters match
+- filters: list of filters
+
+Each filter has to have following fields:
+- pointer: pointer to the JSON field according to [RFC
+  6901](https://tools.ietf.org/html/rfc6901)
+- regex: regular expression which has to match the field pointed to by
+  the pointer
+
+### Configuration paths
+Following locations are checked for a configuration file:
+- `/etc/webhookey/config.yml`
+- `<config_dir>/webhookey/config.yml`
+- `./config.yml`
+
+Whereas `<config_dir>` depends on the platform:
+- Linux:   `$XDG_CONFIG_HOME` or `$HOME/.config`
+- macOS:   `$HOME/Library/Application Support`
+- Windows: `{FOLDERID_RoamingAppData}`
+
+# TODOs
+
+## Systemd service file
+## Use `lazy_static` or `once_cell` for compiled regexes
+## Use `clap` to parse command line arguments
+## Implement the functionality to reply to certain webhooks
+## Security
+### Authentication features
+### Secure cookies?