[Doc] Initial changes to writing_rules.md
[Doc] Initial changes to writing_rules.md

andrejzverev/rspamd,andrejzverev/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,minaevmike/rspamd,AlexeySa/rspamd,andrejzverev/rspamd,andrejzverev/rspamd,minaevmike/rspamd,minaevmike/rspamd,andrejzverev/rspamd,minaevmike/rspamd,minaevmike/rspamd,minaevmike/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,andrejzverev/rspamd,minaevmike/rspamd,minaevmike/rspamd,AlexeySa/rspamd,andrejzverev/rspamd,minaevmike/rspamd,andrejzverev/rspamd