add readme from output of --help

README.txt

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+Pipe through standard input while highlighting and keeping track of delays between lines
+
+Usage: txt-timer [OPTIONS]
+
+Options:
+  -q, --quiet
+          do not output stdin
+  -c, --count <COUNT>
+          number of top differences to print at the end [default: 5]
+  -B, --lines-before <LINES_BEFORE>
+          [default: 5]
+      --color
+          colorized output
+      --color-range <COLOR_RANGE>
+          range for color scale of delay, in seconds [default: 0.2]
+      --time-regex <TIME_REGEX>
+          use regex to extract timestamp from lines instead of using real time, must have one (?<time> ) named capturing group
+      --time-regex-format <TIME_REGEX_FORMAT>
+          format of timestamp, without timezone see `strftime`. Example `%Y-%m-%d %H:%M:%S%.3f`
+  -p, --prepend-time
+          prepend time to output
+  -o, --output-maximals <OUTPUT_MAXIMALS>
+          redirect output of maximum differences to a file
+      --async-buffer-line-count <ASYNC_BUFFER_LINE_COUNT>
+          buffer size for asynchronous processing [default: 128]
+  -h, --help
+          Print help (see more with '--help')