feat(set): adds --file flag to input from a file path

testdata/help-set.ct

@@ -22,6 +22,7 @@ Aliases:
 
 Flags:
   -e, --encrypt        Encrypt the value at rest using age
+  -f, --file string    Read value from a file
   -h, --help           help for set
   -i, --interactive    Prompt before overwriting an existing key
       --safe           Do not overwrite if the key already exists
@@ -48,6 +49,7 @@ Aliases:
 
 Flags:
   -e, --encrypt        Encrypt the value at rest using age
+  -f, --file string    Read value from a file
   -h, --help           help for set
   -i, --interactive    Prompt before overwriting an existing key
       --safe           Do not overwrite if the key already exists

testdata/set-file-conflict-err.ct

@@ -0,0 +1,3 @@
+$ fecho myfile contents
+$ pda set key@sfc value --file myfile --> FAIL
+FAIL  cannot set 'key@sfc': --file and VALUE argument are mutually exclusive

testdata/set-file.ct

@@ -0,0 +1,4 @@
+$ fecho myfile hello from file
+$ pda set key@sf --file myfile
+$ pda get key@sf
+hello from file