Update the contents of NO2 and GRDI content pages. (#40)

* updated the contents for NO2 and GRDI dataset content pages

* resolved the comments

* resolved comments

* resolved further comments

* updated the prose blocks and resolved comments

* Chnaged the measurement units in legend

* Update legend units to include superscript

* Update legend units to include superscript

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Co-authored-by: vishal <vishal.gaur@uah.edu>
Co-authored-by: Slesa Adhikari <slesaad@gmail.com>