Add help for meson format to the man page.

The added help text was derived from the output of the meson help
command much like the markdown online help is derived.

man/meson.1

@@ -608,6 +608,53 @@ Define cpu family for cross compilation.
 \fB\-\-endian {big,little}\fR
 Define endianness for cross compilation.
 
+.SH The format command
+
+.B meson format
+formats a meson source file.
+
+.B meson format [
+.I options
+.B ] [
+.I sources...
+.B ]
+
+.SS "positional arguments:"
+
+.TP
+\fBsources...\fR
+meson source files
+
+.SS "options:"
+
+.TP
+\fB-h, --help\fR
+show this help message and exit
+
+.TP
+\fB-q, --check-only\fR
+exit with 1 if files would be modified by meson format
+
+.TP
+\fB-i, --inplace\fR
+format files in-place
+
+.TP
+\fB-r, --recursive\fR
+recurse subdirs (requires --check-only or --inplace option)
+
+.TP
+\fB-c meson.format, --configuration meson.format\fR
+read configuration from meson.format
+
+.TP
+\fB-e, --editor-config\fR
+try to read configuration from .editorconfig
+
+.TP
+\fB-o OUTPUT, --output OUTPUT\fR
+output file (implies having exactly one input)
+
 .SH EXIT STATUS
 
 .TP