Update basic_searches.md and flags.md

[8dcc]

Changes to search_bytes/basic_searches.md:

• Update output of / Str, / str, fsl and fl commands
• List flag spaces with new fsl instead of old fs
• Select flag space with fs <name> before listing fags with fl (Instead of just running f)
• Use # for rizin comments

Changes to basic_commands/flags.md:

• Update output of fs? and fsl commands
• Replace f-NAME with f- NAME
• Use # for rizin comments