How to export agenda view with html style

[Xiang Ruan]

Hi, all

I am using org-agenda for GTD.
For easy confirming the information on devices like mobile phone, I export my 
agenda view to HTML file which locates at my personal server.

However, the exported html does not have style information. For general org 
file, I know it is easy to add #+HTML_HEADER to specify css information for 
exporting, unfortunately there is no way to add head information in agenda view.

I did some googles, found there are two possible solutions.
One is to use org-agenda-write to store agenda view to org file and add head 
information to the file for exporting.
Though I didn't try it, I believe it work well. However, it is not the way I 
have expected, I want to do it with one step.

I also tried to use org-agenda-export-html-style and did a simple test by 
adding the below code to my .emacs
(setq org-agenda-export-html-style
      "<link rel=\"stylesheet\" 
href=\"https://www.w3schools.com/w3css/4/w3.css\";>
      <link rel='stylesheet' 
href='https://fonts.googleapis.com/css?family=Roboto'>
      <link rel=\"stylesheet\" 
href=\"https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css\";>
)
I found org-agenda-export-html-style inserts text in <style></style> block of 
HTML header that makes the above css including invalid. 

Actually all my personal webpages are made by org-mode with theme-readtheory. 
The org files have head information: 
#+SETUPFILE:  theme-readtheorg.setup

I wonder if I can also include theme-readtheorg.setup in agenda view exporting?

Could somebody help and advice me a good solution?

Thank you in advance.