Repository: prometheus/prometheus (language: go)

Issue:
[Broken Link in Documentation] tsdb README external link.
### What did you do?

In the tsdb [README](https://github.com/prometheus/prometheus/tree/v0.37.0/tsdb), I tried to check the external resources.

### What did you expect to see?

_No response_

### What did you see instead? Under which circumstances?

`A writeup of the original design can be found [here](https://fabxc.org/blog/2017-04-10-writing-a-tsdb/).`

The link in this line is broken.

### System information

_No response_

### Prometheus version

_No response_

### Prometheus configuration file

_No response_

### Alertmanager version

_No response_

### Alertmanager configuration file

_No response_

### Logs

_No response_


Discussion / hints:
Nice catch, thanks for reporting. I guess the site is either down or doesn't exist anymore?
@fabxc will know why :)
I poked him by email to see if he has time, nerves, and motivation to fix his site.

If not, we can point to https://web.archive.org/web/20210803115658/https://fabxc.org/tsdb/ instead.

Fix patch:
diff --git a/tsdb/README.md b/tsdb/README.md
index ad9354586cd..80770e8dd49 100644
--- a/tsdb/README.md
+++ b/tsdb/README.md
@@ -13,7 +13,7 @@ which handles storage and querying of all Prometheus v2 data.
 
 ## External resources
 
-* A writeup of the original design can be found [here](https://fabxc.org/blog/2017-04-10-writing-a-tsdb/).
+* A writeup of the original design can be found [here](https://web.archive.org/web/20210803115658/https://fabxc.org/tsdb/).
 * Video: [Storing 16 Bytes at Scale](https://youtu.be/b_pEevMAC3I) from [PromCon 2017](https://promcon.io/2017-munich/).
 * Compression is based on the Gorilla TSDB [white paper](http://www.vldb.org/pvldb/vol8/p1816-teller.pdf).
 


Test patch: