Fix: Add missing file extensions to source file discovery

Added .f, .f90, and .F90 to the wanted() function in cons script so that
Fortran 77 and Fortran 90 source files are properly discovered during build.

Previously, the file discovery function was missing these extensions, causing
F90 files to be ignored even though the compiler support was in place.

Updated documentation to clarify automatic file discovery.

Co-authored-by: klendathu2k <56083924+klendathu2k@users.noreply.github.com>

Author: Copilot

docs/fortran90-support.md

@@ -44,21 +44,26 @@ Both extensions are mapped to the `build::command::f90` builder in the cons syst
 
 To use Fortran 90 in your project:
 
-1. Create your Fortran 90 source files with `.f90` or `.F90` extensions
-2. Add them to your Conscript file as you would other source files
+1. Create your Fortran 90 source files with `.f90` or `.F90` extensions in your source directory
+2. The cons build system will automatically discover these files when scanning the directory
 3. The build system will automatically use the Fortran 90 compiler for these files
 
-Example:
-```perl
-# In your Conscript file
-my @src = qw(
-    mycode.cxx
-    myfortran.f
-    myfortran90.f90
-);
+**Note**: The build system uses the `find_sources` function to automatically discover source files. As of this update, the following Fortran file extensions are recognized:
+- `.f` - Fortran 77 fixed-form
+- `.F` - Fortran 77 fixed-form with preprocessing
+- `.f90` - Fortran 90 free-form
+- `.F90` - Fortran 90 free-form with preprocessing
 
-Library($env, 'MyLibrary', @src);
+Example directory structure:
 ```
+MyPackage/
+├── mycode.cxx
+├── myfortran.f        # Fortran 77
+├── myfortran90.f90    # Fortran 90
+└── preprocessed.F90   # Fortran 90 with preprocessing
+```
+
+The build system will automatically find all these files and compile them appropriately.
 
 ## Differences from Fortran 77
 

mgr/cons

@@ -1263,9 +1263,12 @@ sub wanted {
       /^\w.*\.cxx$/   ||
       /^\w.*\.cpp$/   ||
       /^\w.*\.g$/     ||
-      /^\w.*\.age$/   || #for STAR      /^\w.*\.f$/       ||
-      /^\w.*\.cdf$/   ||
-      /^\w.*\.F$/) {# print " $File::Find::name\n";
+      /^\w.*\.age$/   ||
+      /^\w.*\.f$/     ||
+      /^\w.*\.F$/     ||
+      /^\w.*\.f90$/   ||
+      /^\w.*\.F90$/   ||
+      /^\w.*\.cdf$/) {# print " $File::Find::name\n";
     push @main::search_files,  $File::Find::name;
   }
 }