feat(docs): update sample.env with full documentation

Author: ThomasBazin

sample.env

@@ -1,11 +1,96 @@
-FRIENDLY_CAPTCHA_SITE_KEY=ABCD1234…
-FRIENDLY_CAPTCHA_API_KEY=EFGH5678…
+# This file is the minimal configuration file used by Dotenv to define the
+# environment variables on localhost.
+#
+# Instructions:
+#   1. copy this file as `.env`
+#   2. edit the `.env` file with working values
+#   3. uncomment the lines to activate or configure associated features
+#
+# Sections:
+#   - friendly captcha
+#   - freescout
+#   - emailing
 
-FREESCOUT_API_URL=<Use your freescout instance URL here, e.g. https://freescout.example.pix.net>
-FREESCOUT_API_KEY=<follow instructions at https://api-docs.freescout.net/>
+# =======
+# FRIENDLY CAPTCHA
+# =======
 
+# Site key provided by Friendly Captcha (account needs to be created). Used to render captcha.
+#
+# If not present, captcha verification will be skipped.
+# 
+# presence: optional
+# type: String
+FRIENDLY_CAPTCHA_SITE_KEY=SITEKEY123456
+
+# API key provided by Friendly Captcha (account needs to be created). Used to verify captcha
+# when submitting form.
+#
+# Needs to be present if FRIENDLY_CAPTCHA_SITE_KEY is present. Error will be thrown
+# when submitting form if not present.
+# 
+# presence: optional but mandatory if FRIENDLY_CAPTCHA_SITE_KEY is present
+# type: String
+FRIENDLY_CAPTCHA_API_KEY=APIKEY123456
+
+# Url to Freescout API
+# 
+# If not present, no conversation will be created to Freescout when submitting forms of type "freescout sending".
+# An error will be displayed in console.
+#
+# presence: optional
+# type: Url
+FREESCOUT_API_URL=https://freescout.example.pix.net
+
+# API key required to call Freescout API
+# 
+# If not present, no conversation will be created to Freescout when submitting forms of type "freescout sending".
+# An error will be displayed in console.
+#
+# presence: optional but mandatory if FREESCOUT_API_URL is present
+# type: String
+FREESCOUT_API_KEY=1234
+
+# =======
+# Emailing
+# =======
+
+# SMTP host Url for mail server
+# 
+# If not present, submitting forms of type "email sending" will throw an error.
+#
+# presence: required
+# type: Url
 SMTP_HOST=localhost
+
+# SMTP Port for mail server
+# 
+# If not present, submitting forms of type "email sending" will throw an error.
+#
+# presence: required
+# type: Number
 SMTP_PORT=1025
+
+# SMTP Secure for mail server
+# 
+# If not present, submitting forms of type "email sending" will throw an error.
+#
+# presence: required
+# type: Boolean
 SMTP_SECURE=false
+
+# SMTP User for mail server
+# 
+# If not present, submitting forms of type "email sending" will throw an error.
+#
+# presence: required
+# type: String
 SMTP_USER=root
-SMTP_PASS=pass
+
+# SMTP Password for mail server
+# 
+# If not present, submitting forms of type "email sending" will throw an error.
+#
+# presence: required
+# type: String
+SMTP_PASS=pass