Create the webhookey manpage

Also add the manpage to the build recipe of the debian package.
This closes #13.

Cargo.toml

@@ -37,6 +37,7 @@ assets = [
        ["config.yml", "etc/webhookey/", "644"],
        ["target/release/webhookey", "usr/bin/", "755"],
        ["README.md", "usr/share/doc/webhookey/README", "644"],
+       ["webhookey.1", "usr/share/man/man1/", "644"],
        ["debian/service", "lib/systemd/system/webhookey.service", "644"],
 ]
 conf-files = ["/etc/webhookey/config.yml"]

webhookey.1

@@ -0,0 +1,57 @@
+.TH WEBHOOKEY 1 "26 Nov 2021" "webhookey" "Linux"
+.SH NAME
+webhookey \- Receive webhooks and act upon them
+.SH SYNOPSIS
+.B webhookey [OPTIONS] [SUBCOMMAND]
+.SH DESCRIPTION
+\fBwebhookey\fR receives http(s) requests in form of webhooks. Those
+webhooks are matched against configured filters. If a filter matches,
+a command (which can also incorporate data contained in the received
+header or body) is executed.
+.SH OPTIONS
+.TP
+.BR "-c", " --config " <FILE>
+Provide a path to the configuration file.
+.TP
+.BR "-h", " --help"
+Print help information.
+.TP
+.BR "-V", " --version"
+Print version information.
+.SH SUBCOMMAND
+.TP
+.B configtest
+- Verifies if the configuration can be parsed without errors.
+.TP
+.B help
+- Print the general help message or the help of the given subcommand(s).
+.SH ENVIRONMENT
+.TP
+.B ROCKET_ADDRESS
+The IP address webhookey listens on (default: 127.0.0.1).
+.TP
+.B ROCKET_PORT
+The port webhookey listens on (default: 8000).
+.TP
+.B ROCKET_WORKERS
+The numbers of threads to use (default: CPU core count).
+.TP
+.B RUST_LOG
+Set the Log level, which can be one one of "error", "warn", "info",
+"debug", "trace" (default: "error").
+.SH EXAMPLES
+.PP
+webhookey configtest
+.RS 4
+Return either "Config is OK" and return code 0 or an error description
+and return code 1.
+.RE
+.PP
+webhookey
+.RS 4
+Start webhookey.
+.RE
+.SH REPORTING BUGS
+To report any bugs file an issue at
+https://git.onders.org/finga/webhookey/issues/new?template=bug.md or
+send an email to <bug-report@onders.org>.