filetype.txt: Update Vim 9.0.0815

Author: tsuyoshicho

en/filetype.txt

@@ -150,6 +150,7 @@ variables can be used to overrule the filetype used for certain extensions:
 	*.fs		g:filetype_fs	|ft-forth-syntax|
 	*.i		g:filetype_i	|ft-progress-syntax|
 	*.inc		g:filetype_inc
+	*.lsl		g:filetype_lsl
 	*.m		g:filetype_m	|ft-mathematica-syntax|
 	*.mod		g:filetype_mod
 	*.p		g:filetype_p	|ft-pascal-syntax|