Reth Book - Stages framework/draft (#360)

* Added framework and start to draft for stages, stopping here to get feedback on approach before pushing forward

* Update README.md

Fixing some wording / grammar.

* Fixing grammar/wording.

* Added note about non-exhaustive stages list, fixed grammar, fixed State exectuion function name, updated language to reflect that the stream yields a SealedHeader and added language to describe that the initial header validation is only a basic validation.

* updated stages chapter, added bodies, senders, execution, next chapter prelude

* typo

* Added line numbers to code snippets for the stages chapter of the reth book

* address reverse header download + other nits

* add note about book hosting

* tweaked wording, formatting

* Address typo "staring"

* Address typo "HeadderDownloader"

* consolidated book.toml

* updating snippets in stages chapter to ignore errors

* template & removed empty fields from book.toml

* addressed build issues, added templating for source code

* only deploy on push to main

* using single quotes in github action if expression

Co-authored-by: Andrew Kirillov <andrew@paradigm.xyz>
Co-authored-by: Andrew Kirillov <20803092+akirillo@users.noreply.github.com>

.github/workflows/book.yml

@@ -25,6 +25,12 @@ jobs:
           curl -sSL https://github.com/rust-lang/mdBook/releases/download/v0.4.14/mdbook-v0.4.14-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=./mdbook
           echo `pwd`/mdbook >> $GITHUB_PATH
 
+      - name: Install mdbook-template
+        run: |
+          mkdir mdbook-template
+          curl -sSL https://github.com/sgoudham/mdbook-template/releases/latest/download/mdbook-template-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=./mdbook-template
+          echo `pwd`/mdbook-template >> $GITHUB_PATH
+
       - name: Run tests
         run: mdbook test
 
@@ -41,6 +47,12 @@ jobs:
           curl -sSL https://github.com/rust-lang/mdBook/releases/download/v0.4.14/mdbook-v0.4.14-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=./mdbook
           echo `pwd`/mdbook >> $GITHUB_PATH
 
+      - name: Install mdbook-template
+        run: |
+          mkdir mdbook-template
+          curl -sSL https://github.com/sgoudham/mdbook-template/releases/latest/download/mdbook-template-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=./mdbook-template
+          echo `pwd`/mdbook-template >> $GITHUB_PATH
+
       - name: Build
         run: mdbook build
 
@@ -50,6 +62,8 @@ jobs:
           path: target/book
 
   deploy:
+    # Only deploy if a push to main
+    if: github.ref_name == 'main' && github.event_name == 'push'
     runs-on: ubuntu-latest
     needs: [test, build]