Add abnormal spacing detection for spam messages

[umputun]

Introduced a new checker to detect abnormal spacing patterns in messages, a common spam evasion technique. It calculates both ratios of short words vs total words as well as ratio of spaces.

The goal is to detect "broken with space" words, i.e. "Th is an exa mple of such cr ap" . The checker configured with this set of options and disabled by default

	AbnormalWords struct {
		Enabled                 bool    `long:"enabled" env:"ENABLED" description:"enable abnormal words check"`
		SpaceRatioThreshold     float64 `long:"ratio" env:"RATIO" default:"0.3" description:"the ratio of spaces to all characters in the message"`
		ShortWordThreshold      int     `long:"short-word" env:"SHORT_WORD" default:"3" description:"the length of the word to be considered short"`
		ShortWordRatioThreshold float64 `long:"short-ratio" env:"SHORT_RATIO" default:"0.7" description:"the ratio of short words to all words in the message"`
	} `group:"space" namespace:"space" env-namespace:"SPACE"`

[cloudflare-workers-and-pages]

Deploying tg-spam with    Cloudflare Pages

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[paskal]

"ExcessiveSpacing" might be better name here and in code.