include benchmarks, add contributing section

README.md

@@ -12,7 +12,7 @@ welcome to use it on your system: it's fast.
 - Fast
 - Really fast
 - Minimal dependencies
-- Actually very fast
+- Actually really fast
 - Cool NixOS logo (other, inferior, distros are not supported)
 - Reliable detection of following info:
   - Hostname/Username
@@ -25,11 +25,45 @@ welcome to use it on your system: it's fast.
   - Memory Usage/Total Memory
   - Storage Usage/Total Storage (for `/` only)
   - Shell Colors
+- Did I mention fast?
+
+## Benchmarks
+
+Microfetch's performance is mostly hardware-dependant, however, the overall
+trend seems to be < 2ms on any modern (2015 and after) CPU. Below are the
+benchmarks with Hyperfine on my desktop system.
+
+| Command                     | Mean [ms] | Min [ms] | Max [ms] | Relative |
+| :-------------------------- | --------: | -------: | -------: | -------: |
+| `target/release/microfetch` | 1.3 ± 0.1 |      1.2 |      3.7 |     1.00 |
+
+On an average configuration, this is roughly 25 times faster than fastfetch and
+around 80 times faster than neofetch. Results, as stated above, may vary.
 
 ## Customizing
 
 You can't.
 
+### Why?
+
+Customization, of any kind, is expensive: I could try reading environment
+variables, parse command-line arguments or read a configuration file but all of
+those increment execution time and resource consumption by a lot.
+
+### Really?
+
+To be fair, you _can_ customize Microfetch by... Well, patching it. It's not the
+best way per se, but it will be the only way that does not compromise on speed.
+
+## Contributing
+
+I will, mostly, reject feature additions. This is not to say you should avoid
+them altogether, as you might have a really good idea worth discussing but as a
+general rule of thumb consider talking to me before creating a feature PR.
+
+Contributions that help improve performance in specific areas of Microfetch are
+welcome. Though, prepare to be bombarded with questions.
+
 ## License
 
 Microfetch is licensed under [GPL3](LICENSE). See the license file for details.