updated pandon-script.sh adds a

-  a cover page. cover.tex file uses the bids logo

- a header with BIDS version number, however, this isn't automated. The header.tex file needs to be updated
for new version release of BIDS specs.

- font change is possible. However, the default LaTex font seemed better to me but can be changed with -V mainfont="DejaVu Serif" or any other
font.

- spacing after 'Quantitative T1rho brain imaging' and before URL on page 21 was modified in the corresponding .md file in the src directory.

merging changes from base repo

- automated header extraction from changelog
- removing all internal links from pdf and replacing them with associated plain text
- modular script but needs to be cleaned up

…ec.pdf

merging most recent upstream commits

updating the fork with most recent upstream commits

Apart from formatting and other minor changes, this commit includes an
initial edit to the .circleci config file to try and build the pdf alongside
circleci build of mkdocs

Final working changes from the following files were imported into this commit:
- ./.circleci/config.yml
- pdf_build_src/build_pdf.sh
- src/04-modality-specific-files/01-magnetic-resonance-imaging-data.md