Ruby CLI: Squelch Processing output when silent is passed in

[mickeytgl]

Fixes #347

Without silent flag:

ruby -I lib exe/herb analyze examples --no-log-file --non-interactive
Processing [1/16]: attributes_with_empty_value.html.erb
Processing [2/16]: begin.html.erb
Processing [3/16]: block.html.erb
Processing [4/16]: case_when.html.erb
Processing [5/16]: comment.html.erb
Processing [6/16]: doctype.html.erb
Processing [7/16]: erb.html.erb
Processing [8/16]: for.html.erb
Processing [9/16]: if_else.html.erb
Processing [10/16]: line-wrap.html.erb
Processing [11/16]: nested_if_and_blocks.html.erb
Processing [12/16]: simple_block.html.erb
Processing [13/16]: simple_erb.html.erb
Processing [14/16]: test.html.erb
Processing [15/16]: until.html.erb
Processing [16/16]: while.html.erb
Completed processing all files.
--- SUMMARY --------------------------------------------------------------------
Total files: 16
✅ Successful: 16 (100.0%)
❌ Failed: 0 (0.0%)
⚠️ Parse errors: 0 (0.0%)
⏱️ Timed out: 0 (0.0%)

⏱️ Total time: 31.9ms

With silent flag:

ruby -I lib exe/herb analyze examples --no-log-file --non-interactive --silent
--- SUMMARY --------------------------------------------------------------------
Total files: 16
✅ Successful: 16 (100.0%)
❌ Failed: 0 (0.0%)
⚠️ Parse errors: 0 (0.0%)
⏱️ Timed out: 0 (0.0%)

⏱️ Total time: 35.15ms

[marcoroth]

Thanks @mickeytgl! 🙏🏼