UPDATE: Add placeholders for all functions

docs/src/functions/fv.md

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+---
+layout: doc
+outline: deep
+lang: en-US
+---
+
+# FV
+
+## Overview
+
+FV (<u>F</u>uture <u>V</u>alue) is a function in the Financial category that can be used to predict the future value of an investment or asset based on its present value.
+
+FV can be used to calculate future value over a specified number of compounding periods. A fixed interest rate or yield is assumed over all periods, and a fixed payment or deposit can be applied at the start or end of every period.
+
+If your interest rate varies between periods, use the **FVSCHEDULE** function instead of FV.
+
+## Parameters
+
+**FV(rate, nper, pmt, pv, period_start)**
+
+- _rate_. The fixed percentage interest rate or yield per period.
+- _nper_. The number of compounding periods to be taken into account. While this will often be an integer, non-integer values are also accepted.
+- _pmt_ (optional). The fixed amount paid or deposited each compounding period (default 0).
+- _pv_ (optional). The present value or starting amount of the asset (default 0).
+- _period_start_ (optional). A logical value indicating whether the payment due dates are at the end (0) of the compounding periods or at the beginning (1) (default 0). FV treats any non-zero value as it would the value 1.
+
+### Additional notes
+
+- FV may generate #ERROR!, #VALUE! or #DIV/0! errors. For more details see our Error Types page (<span style="color:orange">link when page written</span>).
+- Make sure that the _rate_ argument specifies the interest rate or yield applicable to the compounding period, based on the value chosen for _nper_.
+- The _pmt_ and _pv_ arguments should be expressed in the same currency unit. FV returns a value in the same currency unit.
+- To ensure a worthwhile result, one of the _pmt_ and _pv_ arguments should be set to a non-zero value.
+- The setting of the _period_start_ argument only affects the calculation for non-zero values of the _pmt_ argument.
+
+## Details
+
+- If _rate_ = 0, FV solves the equation:
+
+  $$
+  FV = -pv - (pmt \times nper)
+  $$
+
+- If _rate_ <> 0 and _period_start_ = 0, FV solves the equation:
+  $$
+  FV = -pv \times (1 + rate)^{nper} - \dfrac{pmt\times\big({(1+rate)^{nper}-1}\big)}{rate}
+  $$
+- If _rate_ <> 0 and _period_start_ <> 0, FV solves the equation:
+  $$
+  FV = -pv \times (1 + rate)^{nper} - \dfrac{pmt\times\big({(1+rate)^{nper}-1}\big) \times(1+rate)}{rate}
+  $$
+
+## Examples
+
+[See this example in IronCalc](https://app.ironcalc.com/?model=h30aj-o2HyK-1jUR8)
+
+## Links
+
+- For more information about the concept of "future value" in finance, visit Wikipedia's [Future value](https://en.wikipedia.org/wiki/Future_value) page.
+
+- Visit Microsoft Excel's [FV function](https://support.microsoft.com/en-gb/office/fv-function-2eef9f44-a084-4c61-bdd8-4fe4bb1b71b3) page.