Add docu for undocumented functions (#1907)

* Document string manipulation functions

* Document crypto.FNV32a function

* Document functions duration and time.ParseDuration

* Changes according to review feedback

content/en/functions/crypto.FNV32a.md

@@ -0,0 +1,15 @@
+---
+title: crypto.FNV32a
+description: Returns the FNV (Fowler–Noll–Vo) 32 bit hash of a given string.
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: [crypto hash FNV32 Fowler-Noll-Vo]
+signature: ["crypto.FNV32a STRING"]
+aliases: []
+---
+
+This function calculates the 32 bit [FNV1a hash](https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function#FNV-1a_hash) of a given string according to the [specification](https://datatracker.ietf.org/doc/html/draft-eastlake-fnv-12):
+
+    {{ crypto.FNV32a "Hello world" }} → 1498229191

content/en/functions/duration.md

@@ -0,0 +1,32 @@
+---
+title: duration
+description: Returns a `time.Duration` structure, using the given time unit and duration number.
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: [time duration]
+signature: ["duration TIME_UNIT DURATION_NUMBER"]
+aliases: []
+---
+
+`time.Duration` converts a given number into a [`time.Duration`](https://pkg.go.dev/time#Duration) structure so you can access its fields. E.g. you can perform [time operations](https://pkg.go.dev/time#Duration) on the returned `time.Duration` value:
+
+    {{ printf "There are %.0f seconds in one day." (duration "hour" 24).Seconds }}
+    <!-- Output: There are 86400 seconds in one day. -->
+
+Make your code simpler to understand by using a [chained pipeline](https://pkg.go.dev/text/template#hdr-Pipelines):
+
+    {{ mul 7.75 60 | duration "minute" }} → 7h45m0s
+    {{ mul 120 60 | mul 1000 | duration "millisecond" }} → 2h0m0s
+
+You have to specify a time unit for the number given to the function. Valid time units are:
+
+Duration|Valid time units
+:--|:--
+hours|`hour`, `h`
+minutes|`minute`, `m`
+seconds|`second`, `s`
+milliseconds|`millisecond`, `ms`
+microseconds|`microsecond`, `us`, `µs`
+nanoseconds|`nanosecond`, `ns`

content/en/functions/lower.md

@@ -10,7 +10,9 @@ menu:
   docs:
     parent: "functions"
 keywords: [strings,casing]
-signature: ["lower INPUT"]
+signature:
+  - "lower INPUT"
+  - "strings.ToLower INPUT"
 workson: []
 hugoversion:
 relatedfuncs: []
@@ -18,6 +20,10 @@ deprecated: false
 aliases: []
 ---
 
-```
-{{lower "BatMan"}} → "batman"
+
+Note that `lower` can be applied in your templates in more than one way:
+
+```go-html-template
+{{ lower "BatMan" }} → "batman"
+{{ "BatMan" | lower }} → "batman"
 ```

content/en/functions/strings.Contains.md

@@ -0,0 +1,18 @@
+---
+title: strings.Contains
+description: Reports whether a string contains a substring.
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: [string strings substring contains]
+signature: ["strings.Contains STRING SUBSTRING"]
+aliases: []
+relatedfuncs: [strings.ContainsAny]
+---
+
+    {{ strings.Contains "Hugo" "go" }} → true
+
+The check is case sensitive: 
+
+    {{ strings.Contains "Hugo" "Go" }} → false

content/en/functions/strings.ContainsAny.md

@@ -0,0 +1,18 @@
+---
+title: strings.ContainsAny
+description: Reports whether a string contains any character from a given string.
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: [string strings substring contains any]
+signature: ["strings.ContainsAny STRING CHARACTERS"]
+aliases: []
+relatedfuncs: [strings.Contains]
+---
+
+    {{ strings.ContainsAny "Hugo" "gm" }} → true
+
+The check is case sensitive: 
+
+    {{ strings.ContainsAny "Hugo" "Gm" }} → false

content/en/functions/time.ParseDuration.md

@@ -0,0 +1,20 @@
+---
+title: time.ParseDuration
+description: Parses a given duration string into a `time.Duration` structure.
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: [time parse duration]
+signature: ["time.ParseDuration DURATION"]
+hugoversion:
+aliases: []
+---
+
+`time.ParseDuration` parses a duration string into a [`time.Duration`](https://pkg.go.dev/time#Duration) structure so you can access its fields.
+A duration string is a possibly signed sequence of decimal numbers, each with optional fraction and a unit suffix, such as `300ms`, `-1.5h` or `2h45m`. Valid time units are `ns`, `us` (or `µs`), `ms`, `s`, `m`, `h`.
+
+You can perform [time operations](https://pkg.go.dev/time#Duration) on the returned `time.Duration` value:
+
+    {{ printf "There are %.0f seconds in one day." (time.ParseDuration "24h").Seconds }}
+    <!-- Output: There are 86400 seconds in one day. -->

content/en/functions/upper.md

@@ -11,7 +11,9 @@ menu:
   docs:
     parent: "functions"
 toc:
-signature: ["upper INPUT"]
+signature:
+  - "upper INPUT"
+  - "strings.ToUpper INPUT"
 workson: []
 hugoversion:
 relatedfuncs: []