feat(funcs): add semver functions (#1829)

* feat(funcs): add semver functions

- semver.Version: new a SemVer struct.
- semver.MatchConstraint: match in arg with semver constraint string.

refer to: https://github.com/Masterminds/sprig/blob/master/semver.go

* docs(functions): add documents for semver functions

* Update docs-src/content/functions/semver.yaml

Co-authored-by: Dave Henderson <dhenderson@gmail.com>

* fix(funcs,docs,docs-src): fix the reviewing issues

---------

Co-authored-by: Dave Henderson <dhenderson@gmail.com>

1 files changed, 85 insertions, 0 deletions

diff --git a/docs/content/functions/semver.md b/docs/content/functions/semver.md
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+---
+title: semver functions
+menu:
+  main:
+    parent: functions
+---
+
+These functions allow user you to parse a [semantic version](http://semver.org/) string or test it with constraint.
+
+It's implemented with the https://github.com/Masterminds/semver library.
+
+## `semver.Semver`_(unreleased)_
+**Unreleased:** _This function is in development, and not yet available in released builds of gomplate._
+
+Returns a semantic version struct holding the `input` version string.
+
+The returned struct are defined at: [`semver.Version`](https://pkg.go.dev/github.com/Masterminds/semver/v3#Version).
+
+### Usage
+
+```
+semver.Semver input
+```
+```
+input | semver.Semver
+```
+
+### Arguments
+
+| name | description |
+|------|-------------|
+| `input` | _(required)_ The input to parse |
+
+### Examples
+
+```console
+$ gomplate -i '{{ semver.Semver "v1.1.1"}}'
+1.1.1
+```
+```console
+$ gomplate -i '{{ (semver.Semver "v1.1.1").Major }}'
+1
+```
+```console
+$ gomplate -i 'the pre release version is {{ ("v1.1.1" | semver.Semver).SetPrerelease "beta.1" }}'
+the pre release version is 1.1.1-beta.1
+```
+
+## `semver.CheckConstraint`_(unreleased)_
+**Unreleased:** _This function is in development, and not yet available in released builds of gomplate._
+
+Test whether the input version matchs the constraint.
+
+Ref: https://github.com/Masterminds/semver#checking-version-constraints
+
+### Usage
+
+```
+semver.CheckConstraint constraint input
+```
+```
+input | semver.CheckConstraint constraint
+```
+
+### Arguments
+
+| name | description |
+|------|-------------|
+| `constraint` | _(required)_ The constraints expression to test. |
+| `input` | _(required)_ The input semantic version string to test. |
+
+### Examples
+
+```console
+$ gomplate -i '{{ semver.CheckConstraint "> 1.0" "v1.1.1" }}'
+true
+```
+```console
+$ gomplate -i '{{ semver.CheckConstraint "> 1.0, <1.1" "v1.1.1" }}'
+false
+```
+```console
+$ gomplate -i '{{ "v1.1.1" | semver.CheckConstraint "> 1.0" }}'
+true
+```