update readme: up ubuntu version to 22.04 and add C standard

readme.md

@@ -7,11 +7,11 @@
 [![Hits-of-Code](https://hitsofcode.com/github/polystat/c2eo)](https://hitsofcode.com/view/github/polystat/c2eo)
 [![license](https://img.shields.io/github/license/polystat/c2eo?color=e6e6e6)](https://github.com/polystat/c2eo/blob/master/license.txt)
 
-This is a experimental translator of [C](https://en.wikipedia.org/wiki/C_(programming_language)) programs to [EO](https://www.eolang.org) programs.
+This is a experimental translator of C ([ISO/IEC 9899:2018](https://www.iso.org/standard/74528.htm)) programs to [EO](https://www.eolang.org) programs.
 
 ## How to Use
 
-Assuming, you are on [Ubuntu 20+](https://ubuntu.com/download):
+Assuming, you are on [Ubuntu 22.04+](https://ubuntu.com/download):
 
 ```bash
 $ apt update
@@ -42,7 +42,7 @@ However, you can try to build the project from source at your own risk.
 
 ## How to Contribute
 
-Again, we recommend [Ubuntu 20+](https://ubuntu.com/download) and you will need
+Again, we recommend [Ubuntu 22.04+](https://ubuntu.com/download) and you will need
 [wget 1.21+](https://www.tecmint.com/install-wget-in-linux/), 
 [tar 1.30+](https://www.tecmint.com/install-tar-in-centos-rhel-and-fedora/), 
 [git 2.32.+](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git),