lib: Add fortnightly as a synonym for biweekly.

hledger-lib/Hledger/Data/Dates.hs

@@ -984,6 +984,8 @@ reportingintervalp = choice' [
                        tryinterval "year"    "yearly"    Years,
                        do string' "biweekly"
                           return $ Weeks 2,
+                       do string' "fortnightly"
+                          return $ Weeks 2,
                        do string' "bimonthly"
                           return $ Months 2,
                        do string' "every"

hledger/hledger.1

@@ -1521,7 +1521,7 @@ T}
 .TE
 .PP
 The following more complex report intervals are also supported:
-\f[C]biweekly\f[R], \f[C]bimonthly\f[R],
+\f[C]biweekly\f[R], \f[C]fortnightly\f[R], \f[C]bimonthly\f[R],
 \f[C]every day|week|month|quarter|year\f[R],
 \f[C]every N days|weeks|months|quarters|years\f[R].
 .PP

hledger/hledger.m4.md

@@ -1029,6 +1029,7 @@ For example:
 
 The following more complex report intervals are also supported:
 `biweekly`,
+`fortnightly`,
 `bimonthly`,
 `every day|week|month|quarter|year`,
 `every N days|weeks|months|quarters|years`.