feat: Add [DOMAIN_EXPIRATION] placeholder for monitoring domain expiration using WHOIS (#325)

* feat: Add [DOMAIN_EXPIRATION] placeholder for monitoring domain expiration using WHOIS

* test: Fix issue caused by possibility of millisecond elapsed during previous tests

* test: Fix test with different behavior based on architecture

* docs: Revert accidental change to starttls example

* docs: Fix mistake in comment for Condition.hasIPPlaceholder()

vendor/github.com/TwiN/whois/README.md

@@ -0,0 +1,65 @@
+# whois
+![test](https://github.com/TwiN/whois/workflows/test/badge.svg?branch=master)
+
+Lightweight library for retrieving WHOIS information on a domain.
+
+It automatically retrieves the appropriate WHOIS server based on the domain's TLD by first querying IANA.
+
+
+## Usage
+### As an executable
+To install it:
+```console
+go install github.com/TwiN/whois/cmd/whois@latest
+```
+To run it:
+```console 
+whois example.com
+```
+
+### As a library
+```console
+go get github.com/TwiN/whois
+```
+
+#### Query
+If all you want is the text a WHOIS server would return you, you can use the `Query` method of the `whois.Client` type:
+```go
+package main
+
+import "github.com/TwiN/whois"
+
+func main() {
+    client := whois.NewClient()
+    output, err := client.Query("example.com")
+    if err != nil {
+    	panic(err)
+    }
+    println(output)
+}
+```
+
+#### QueryAndParse
+If you want specific pieces of information, you can use the `QueryAndParse` method of the `whois.Client` type:
+```go
+package main
+
+import "github.com/TwiN/whois"
+
+func main() {
+    client := whois.NewClient()
+    response, err := client.QueryAndParse("example.com")
+    if err != nil {
+    	panic(err)
+    }
+    println(response.ExpirationDate.String()) 
+}
+```
+Note that because there is no standardized format for WHOIS responses, this parsing may not be successful for every single TLD.
+
+Currently, the only fields parsed are:
+- `ExpirationDate`: The time.Time at which the domain will expire
+- `DomainStatuses`: The statuses that the domain currently has (e.g. `clientTransferProhibited`)
+- `NameServers`: The nameservers currently tied to the domain
+
+If you'd like one or more other fields to be parsed, please don't be shy and create an issue or a pull request.