Delimit with "end of word" the regexes for the keywords "pi" and "sigma".

[maggesi]

How to detect the problem:
type in an Elpi file a word containing internally the substring pi (or sigma), such as
typing and see the colouration of the "pi".

Notice that this problem often breaks the syntax detection of the rest of the file.

[gares]

It should be fixed. I'll push the new version to the app store soon, in the meanwhile you can usa a symlink to a checkout of this repo as in:

gares@ollypat:~/LPCIC/coq-elpi-lang$ ls -l ~/.vscode-oss/extensions/
...
lrwxrwxrwx  1 gares gares   28 sept.  6 17:12 elpi-lang -> /home/gares/LPCIC/elpi-lang/
...