docs: update .vuepress/config.js (#5043)

## Description

![image](https://user-images.githubusercontent.com/1021101/86193320-7aa13200-bb00-11ea-95ac-aa6468ab7f46.png)


### Next steps:
- [x] bump vuepress-theme-cosmos version
- [x] tweak config.js
- [x] update color variables
- [x] sh, shell → bash for syntax highlighting

docs/tendermint-core/light-client-protocol.md

@@ -38,7 +38,7 @@ https://pkg.go.dev/github.com/tendermint/tendermint/light?tab=doc#TrustOptions
 One way to obtain semi-trusted hash & height is to query multiple full nodes
 and compare their hashes:
 
-```sh
+```bash
 $ curl -s https://233.123.0.140:26657:26657/commit | jq "{height: .result.signed_header.header.height, hash: .result.signed_header.commit.block_id.hash}"
 {
   "height": "273",
@@ -54,7 +54,7 @@ can be tracked back to a block header by a proof will be verified before
 passing them back to the caller. Other than that, it will present the same
 interface as a full Tendermint node.
 
-```sh
+```bash
 $ tendermint light supernova -p tcp://233.123.0.140:26657 \
   -w tcp://179.63.29.15:26657,tcp://144.165.223.135:26657 \
   --height=10 --hash=37E9A6DD3FA25E83B22C18835401E8E56088D0D7ABC6FD99FCDC920DD76C1C57