fix: init command build empty config file (#108)

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## Description
<!-- Small description -->

This PR intends to fix the init command building empty config instead of
the default config since `bytes` value of `DefaultConfig` built by
constructor is `nil`.

## Checklist
- [x] Targeted PR against correct branch.
- [ ] Linked to Github issue with discussion and accepted design OR link
to spec that describes this work.
- [ ] Wrote unit tests.
- [x] Re-reviewed `Files changed` in the Github PR explorer.

types/config/config.go

@@ -3,6 +3,8 @@ package config
 import (
 	"strings"
 
+	"gopkg.in/yaml.v3"
+
 	databaseconfig "github.com/forbole/juno/v4/database/config"
 	loggingconfig "github.com/forbole/juno/v4/logging/config"
 	nodeconfig "github.com/forbole/juno/v4/node/config"
@@ -41,11 +43,19 @@ func NewConfig(
 }
 
 func DefaultConfig() Config {
-	return NewConfig(
+	cfg := NewConfig(
 		nodeconfig.DefaultConfig(),
 		DefaultChainConfig(), databaseconfig.DefaultDatabaseConfig(),
 		parserconfig.DefaultParsingConfig(), loggingconfig.DefaultLoggingConfig(),
 	)
+
+	bz, err := yaml.Marshal(cfg)
+	if err != nil {
+		panic(err)
+	}
+
+	cfg.bytes = bz
+	return cfg
 }
 
 func (c Config) GetBytes() ([]byte, error) {