Add convert docs

Author: jakobkmar

guide/docs/convert.md

@@ -0,0 +1,25 @@
+# Convert
+
+## To an email object
+
+EML `String` to `Email`
+```kotlin
+string.toEmail()
+```
+
+`MimeMessage` to `Email`
+```kotlin
+mimeMessage.email
+```
+
+## From an email object
+
+`Email` to `MimeMessage`
+```kotlin
+email.mimeMessage
+```
+
+`Email` to EML `String`
+```kotlin
+email.eml
+```

guide/mkdocs.yml

@@ -18,6 +18,7 @@ nav:
   - Core:
       - Email API: core.md
       - Kotlin HTML DSL: html.md
+      - Convert: convert.md
   - Server: server.md
   - Client: client.md
   - TLS: tls.md