Add '.' to characters permitted in man page titles

.gitignore

@@ -1,3 +1,4 @@
 .build
 scdoc
 scdoc.1
+scdoc.5

src/main.c

@@ -71,7 +71,7 @@ static void parse_preamble(struct parser *p) {
 	struct tm *now_tm = localtime(&now);
 	strftime(date, sizeof(date), "%F", now_tm);
 	while ((ch = parser_getch(p)) != UTF8_INVALID) {
-		if ((ch < 0x80 && isalnum(ch)) || ch == '_' || ch == '-') {
+		if ((ch < 0x80 && isalnum(ch)) || ch == '_' || ch == '-' || ch == '.') {
 			assert(str_append_ch(name, ch) != -1);
 		} else if (ch == '(') {
 			section = parse_section(p);