feat: load config from env vars (#576)

Signed-off-by: Nico <nico.macioszek@gmail.com>

crates/core/config/src/lib.rs

@@ -1,7 +1,7 @@
 use std::{collections::HashMap, path::Path};
 
 use cached::proc_macro::cached;
-use config::{Config, File, FileFormat};
+use config::{Config, Environment, File, FileFormat};
 use futures_locks::RwLock;
 use once_cell::sync::Lazy;
 use serde::Deserialize;
@@ -109,6 +109,8 @@ static CONFIG_BUILDER: Lazy<RwLock<Config>> = Lazy::new(|| {
             cwd = path.parent();
         }
 
+        builder = builder.add_source(Environment::with_prefix("REVOLT").separator("__"));
+
         builder.build().unwrap()
     })
 });