feat: convert from mdbook to Grav format

- Rename src/ to pages/
- Add Grav frontmatter to markdown files
- Create numbered folder structure
- Remove mdbook-specific files

Migration from mdbook to Grav CMS.

src/SUMMARY.md

@@ -1,3 +0,0 @@
-# Introduction
-
-- [Introduction](./introduction.md)

src/introduction.md

@@ -1,17 +0,0 @@
-# Side Door (Solutions) Group - Business/Operations/Product Plan - Introduction
-
-## Executive Summary for Side Door (Solutions) Group
-
-(pending formal review for 501c3/c4/(super)PAC packaging as appropriate, but general idea outlined below )
-
-- (Super)PAC for candidates that support the mission of the TSYS Group
-- 501c4 as a service (SideDoorGroup)
-- TX non profit corporations with intent to become 501c4/(super)PAC
-- Call to action/activism as a service (Side Door Solutions Group)
-
-# Reduction to practice
-
-- [GIT Organization](https://git.knownelement.com/SideDoorGroup) (may be split into SDG/SDSG pending formal review)
-- [Discourse category](https://community.turnsys.com/c/nonprofit/chiefcommonsofficer-sidedoorgroup/14) (may be split into SDG/SDSG pending formal review)
-- [Side Door Group Redmine Project](https://projects.knownelement.com/projects/sidedoorgroup)
-- [Side Door Solutions Group Redmine Project](https://projects.knownelement.com/projects/side-door-solutions-group)