Update readme for distributed systems module

Author: alexbozhenko

07_distributed_systems/01_intro/.vscode/launch.json 07_distributed_systems/.vscode/launch.json

@@ -0,0 +1,39 @@
+Description of the module from the official [csi page](https://bradfieldcs.com/csi/):
+> Understanding principles and practical considerations for building high-scale data-intensive applications, and learning to reason about tradeoffs between fault tolerance, latency, throughput, consistency and operational overhead.
+
+This folder contains "Distributed" key-value store built for educational purposes, inspired by ideas used in DynamoDB:
+- Custom binary format for storing the data on disk and sending KV pairs over the network
+- Replications
+- Partitioning using Consistent hashing
+- Servers register themselves with `etcd`, and clients are made aware of currenly alive server by pulling that data from `etcd`.
+
+Usage:
+1. Start 3 server nodes in separate windows, each responsible for 
+```
+server$ go run . primary_partition 0
+server$ go run . primary_partition 1
+server$ go run . primary_partition 2
+```
+
+2. Start clients in other windows:
+```
+client$ go run .
+Welcome to the distributed K-V store client
+We support the following syntax:
+get foo
+set foo=bar
+
+In [1]: get foo
+Out[1]: foofoo
+...
+```
+You can also run expect script:
+```
+client$ go build; expect expect_script_primary.exp 8000
+```
+Or do it in parallel with `clush`:
+```
+client$ go build; clush -f 100  -R exec -w [1-10] expect expect_script_primary.exp 8000
+```
+
+In server logs you will see that requests are redirected using consistent hashing algorithm.