docs: template reference (#1653)

* chore: deprecation warnings for template functions

* docs: update reference pages

website/docs/usage.mdx

@@ -966,8 +966,9 @@ you're interested in this functionality, we would appreciate your feedback.
 
 :::
 
-Variables can be set in many places in a Taskfile. When executing templates,
-Task will look for variables in the order listed below (most important first):
+Variables can be set in many places in a Taskfile. When executing
+[templates][templating-reference], Task will look for variables in the order
+listed below (most important first):
 
 - Variables declared in the task definition
 - Variables given while calling a task from another (See
@@ -1383,81 +1384,6 @@ commands are executed in the reverse order if you schedule multiple of them.
 
 :::
 
-## Go's template engine
-
-Task parse commands as [Go's template engine][gotemplate] before executing them.
-Variables are accessible through dot syntax (`.VARNAME`).
-
-All functions by the Go's
-[slim-sprig lib](https://go-task.github.io/slim-sprig/) are available. The
-following example gets the current date in a given format:
-
-```yaml
-version: '3'
-
-tasks:
-  print-date:
-    cmds:
-      - echo {{now | date "2006-01-02"}}
-```
-
-Task also adds the following functions:
-
-- `OS`: Returns the operating system. Possible values are `windows`, `linux`,
-  `darwin` (macOS) and `freebsd`.
-- `ARCH`: return the architecture Task was compiled to: `386`, `amd64`, `arm` or
-  `s390x`.
-- `splitLines`: Splits Unix (`\n`) and Windows (`\r\n`) styled newlines.
-- `catLines`: Replaces Unix (`\n`) and Windows (`\r\n`) styled newlines with a
-  space.
-- `toSlash`: Does nothing on Unix, but on Windows converts a string from `\`
-  path format to `/`.
-- `fromSlash`: Opposite of `toSlash`. Does nothing on Unix, but on Windows
-  converts a string from `/` path format to `\`.
-- `exeExt`: Returns the right executable extension for the current OS (`".exe"`
-  for Windows, `""` for others).
-- `shellQuote` (aliased to `q`): Quotes a string to make it safe for use in shell scripts. Task
-  uses [this Go function](https://pkg.go.dev/mvdan.cc/sh/v3@v3.4.0/syntax#Quote)
-  for this. The Bash dialect is assumed.
-- `splitArgs`: Splits a string as if it were a command's arguments. Task uses
-  [this Go function](https://pkg.go.dev/mvdan.cc/sh/v3@v3.4.0/shell#Fields)
-- `joinPath`: Joins any number of arguments into a path. The same as Go's
-  [filepath.Join](https://pkg.go.dev/path/filepath#Join).
-- `relPath`: Converts an absolute path (second argument) into a relative path,
-  based on a base path (first argument). The same as Go's
-  [filepath.Rel](https://pkg.go.dev/path/filepath#Rel).
-- `merge`: Creates a new map that is a copy of the first map with the keys of
-  each subsequent map merged into it. If there is a duplicate key, the value of
-  the last map with that key is used.
-- `spew`: Returns the Go representation of a specific variable. Useful for
-  debugging. Uses the [davecgh/go-spew](https://github.com/davecgh/go-spew)
-  package.
-
-Example:
-
-```yaml
-version: '3'
-
-tasks:
-  print-os:
-    cmds:
-      - echo '{{OS}} {{ARCH}}'
-      - echo '{{if eq OS "windows"}}windows-command{{else}}unix-command{{end}}'
-      # This will be path/to/file on Unix but path\to\file on Windows
-      - echo '{{fromSlash "path/to/file"}}'
-  enumerated-file:
-    vars:
-      CONTENT: |
-        foo
-        bar
-    cmds:
-      - |
-        cat << EOF > output.txt
-        {{range $i, $line := .CONTENT | splitLines -}}
-        {{printf "%3d" $i}}: {{$line}}
-        {{end}}EOF
-```
-
 ## Help
 
 Running `task --list` (or `task -l`) lists all tasks with a description. The
@@ -1996,4 +1922,5 @@ if called by another task, either directly or as a dependency.
 {/* prettier-ignore-start */}
 [gotemplate]: https://golang.org/pkg/text/template/
 [map-variables]: ./experiments/map_variables.mdx
+[templating-reference]: ./reference/templating.mdx
 {/* prettier-ignore-end */}