README: Update line-length error to 100 chars

Today I was reminded again that the current line length limit isn't 80
chars, but 100 chars, so I wanted to submit a PR to fix that in the
original repo, only to find someone else already did (PR 25).
And that's when I found this repo.
While the rule was updated, the README wasn't, so do that now.

Note that the current upstream 'Linux kernel coding style' does NOT
mention the 100 char limit, but only mentions the preferred max length
of 80.

Signed-off-by: Diederik de Haas <[email protected]>
Link: vivien#25
Link: https://git.kernel.org/linus/bdc48fa11e46f867ea4d75fa59ee87a7f48be144

Author: diederikdehaas

README.md

@@ -5,7 +5,7 @@ described at: https://www.kernel.org/doc/Documentation/process/coding-style.rst
 
 It will automatically apply known rules to kernel related files, such as .c,
 .h, Kconfig and patch files. The main rules are about indentation and syntax
-error highlighting (like exceeding 80 chars).
+error highlighting (like exceeding 100 chars).
 
 The original plugin was written by Vivien Didelot, developed in this
 [Github repository](https://github.com/vivien/vim-linux-coding-style) and availble