Update the binary classifier cataloger developer README to match the
current workflow:
- Testing section used the non-existent flag -must-use-full-binaries
against .../testdata/...; the real flag is -must-use-original-binaries
and Test_Cataloger_PositiveCases lives in the binary package. Fix the
command and add a single-fixture variant.
- Point add-snippet references at the make target and note the (Y/n/q)
prompt requires y to write the snippet.
- Fix the test file name (classifier_cataloger_test.go) and document the
go generate ./internal/capabilities step for new classifiers.
Fixes#4510
Signed-off-by: alliasgher <alliasgher123@gmail.com>
