Add link to Erasure Code Calculator (#88)

Author: brawer

docs/features/distributed/index.md

@@ -15,6 +15,6 @@ RustFS can run anywhere and on any cloud, but typically runs on commodity server
 
 RustFS atomically writes data and metadata, eliminating the need for a separate metadata database. Additionally, RustFS performs all functionality (erasure coding, bitrot checking, encryption) as inline, strictly consistent operations. This results in extraordinary resilience.
 
-Each RustFS cluster is a collection of distributed RustFS servers, with one process per node. RustFS runs as a single process in user space and uses lightweight coroutines to achieve high concurrency. Drives are grouped into erasure sets (see the erasure calculator here), and objects are placed on these sets using a deterministic hashing algorithm.
+Each RustFS cluster is a collection of distributed RustFS servers, with one process per node. RustFS runs as a single process in user space and uses lightweight coroutines to achieve high concurrency. Drives are grouped into erasure sets (see the [erasure code calculator](https://rustfs.com/erasure-code-calculator/)), and objects are placed on these sets using a deterministic hashing algorithm.
 
 RustFS is designed for large-scale, multi-datacenter cloud storage services. Each tenant runs their own RustFS cluster, completely isolated from other tenants, enabling them to protect themselves from any disruption due to upgrades, updates, and security events. Each tenant scales independently by federating clusters across geographies.