Refactor environment files and update .gitignore

Environment variable definitions were moved from .env.development, .env.test and .env.production to a new shared .env file. This provides a centralized location for common environment variables values, easier manageability, and overrides capability in specific environments. The .gitignore file was also updated to no longer ignore the .env file as this file now contains public / non-sensitive configuration values.

apps/web/.env

@@ -0,0 +1,35 @@
+# SHARED ENVIROMENT VARIABLES
+# HERE YOU CAN ADD ALL THE **PUBLIC** ENVIRONMENT VARIABLES THAT ARE SHARED ACROSS ALL THE ENVIROMENTS
+# PLEASE DO NOT ADD ANY CONFIDENTIAL KEYS OR SENSITIVE INFORMATION HERE
+# ONLY CONFIGURATION, PATH, FEATURE FLAGS, ETC.
+# TO OVERRIDE THESE VARIABLES IN A SPECIFIC ENVIRONMENT, PLEASE ADD THEM TO THE SPECIFIC ENVIRONMENT FILE (e.g. .env.development, .env.production)
+
+# SITE
+NEXT_PUBLIC_SITE_URL=http://localhost:3000
+NEXT_PUBLIC_PRODUCT_NAME=Makerkit
+NEXT_PUBLIC_SITE_TITLE="Makerkit - The easiest way to build and manage your SaaS"
+NEXT_PUBLIC_SITE_DESCRIPTION="Makerkit is the easiest way to build and manage your SaaS. It provides you with the tools you need to build your SaaS, without the hassle of building it from scratch."
+NEXT_PUBLIC_DEFAULT_THEME_MODE=light
+NEXT_PUBLIC_THEME_COLOR="#ffffff"
+NEXT_PUBLIC_THEME_COLOR_DARK="#0a0a0a"
+
+# CMS
+CMS_CLIENT=keystatic
+
+# KEYSTATIC
+NEXT_PUBLIC_KEYSTATIC_CONTENT_PATH=./content
+
+# LOCALES PATH
+NEXT_PUBLIC_LOCALES_PATH=apps/web/public/locales
+
+# PATHS (to be used in "packages")
+SIGN_IN_PATH=/auth/sign-in
+SIGN_UP_PATH=/auth/sign-up
+TEAM_ACCOUNTS_HOME_PATH=/home
+INVITATION_PAGE_PATH=/join
+
+# FEATURE FLAGS
+NEXT_PUBLIC_ENABLE_ACCOUNT_DELETION=true
+NEXT_PUBLIC_ENABLE_PERSONAL_ACCOUNT_BILLING=true
+NEXT_PUBLIC_ENABLE_ORGANIZATION_DELETION=true
+NEXT_PUBLIC_ENABLE_ORGANIZATION_BILLING=true