add intro slides and update readme

Author: JessicaS11

01.IntroductorySession_slides.pdf

@@ -13,12 +13,12 @@ These tutorials were largely developed by volunteer instructors. Each tutorial w
 ## Re-create the icesat2 hackweek JupyterLab environment with Pangeo Binder
 
 ## Tutorials
-### Introductory Session (slides)
+### 01. Introductory Session (slides)
 *Anthony Arendt and Charley Haley*
 
-[Slides](https://docs.google.com/presentation/d/1kNc6u4mz9qt5TI-DCosSL6jZ5M7q_k3godlBrOE891c/edit?usp=sharing)
+    * [Slides](https://docs.google.com/presentation/d/1kNc6u4mz9qt5TI-DCosSL6jZ5M7q_k3godlBrOE891c/edit?usp=sharing)
 
-### ICESat-2 Mission: Satellite, Sensor, and Data
+### 02. ICESat-2 Mission: Satellite, Sensor, and Data
 *Axel Schweiger*
 
 * Welcome by the NASA Cryosphere Program Manager (*Thorsten Markus*)
@@ -27,25 +27,26 @@ These tutorials were largely developed by volunteer instructors. Each tutorial w
 * ICESat-2 data products (*Ben Smith*)
     * [Slides](https://github.com/ICESAT-2HackWeek/intro_ICESat2/blob/master/ICESat-2_data_products_Hackweek2020.pptx)
 
-### Git and GitHub
+### 03. Git and GitHub
 *Fernando Perez*
 
 [intro-git](https://github.com/ICESAT-2HackWeek/intro-git)
+
 [Slides](https://docs.google.com/presentation/d/1pOWte7V5UbnVBvRktvLbLTRluDwrGbXtIdAZhzAd1AE/edit?usp=sharing)
 
-### Jupyter and iPython
+### 04. Jupyter and iPython
 *Fernando Perez*
 
-[intro-jupyter](https://github.com/ICESAT-2HackWeek/intro-jupyter)
-[Slides](https://docs.google.com/presentation/d/1TfY7rnCuGQDrlvsf2-P9lNADT2vwiJsdb7vmgZ3SDmA/edit?usp=sharing)
+    * [intro-jupyter](https://github.com/ICESAT-2HackWeek/intro-jupyter)
+    * [Slides](https://docs.google.com/presentation/d/1TfY7rnCuGQDrlvsf2-P9lNADT2vwiJsdb7vmgZ3SDmA/edit?usp=sharing)
 
 
-### overview of python / numpy / pandas / matplotlib / geospatial data processing
+### 05. overview of python / numpy / pandas / matplotlib / geospatial data processing
 *David Shean*
 
 [geospatial-analysis](https://github.com/ICESAT-2HackWeek/geospatial-analysis)
 
-### Introduction to ICESat-2 Sea Ice and Land Ice Products and Data Access
+### 06. Introduction to ICESat-2 Sea Ice and Land Ice Products and Data Access
 
 * Sea ice products: overview of products, algorithms, and parameters for sea ice investigations (*Alek Petty*)
 
@@ -57,32 +58,32 @@ These tutorials were largely developed by volunteer instructors. Each tutorial w
 
 * [data access lesson](https://nbviewer.jupyter.org/github/ICESAT-2HackWeek/data-access/blob/master/notebooks/01-Data_Resources_Intro.ipynb)
 
-### Programmatic ICESat-2 data access
+### 07. Programmatic ICESat-2 data access
 *Jessica Scheick and Amy Steiker*
 
 [Programmatic ICESat-2 data access](https://github.com/ICESAT-2HackWeek/data-access)
 
-### Introduction to HDF5 and ICESat-2 data files
+### 08. Introduction to HDF5 and ICESat-2 data files
 *Fernando Paolo*
 
 [Introduction to HDF5 and ICESat-2 data files](https://github.com/ICESAT-2HackWeek/intro-hdf5)
 
-### Land ice applications
+### 09. Land ice applications
 *Ben Smith*
 
 [Land ice applications](https://github.com/ICESAT-2HackWeek/Land_Ice_Applications)
 
-### Sea ice applications
+### 10. Sea ice applications
 *Ellen Buckley*
 
  [Sea ice applications](https://github.com/ICESAT-2HackWeek/sea-ice-tutorials)
 
- ### Science data generation
+ ### 11. Science data generation
  *Johan Nilsson*
 
  [Science data generation](https://github.com/ICESAT-2HackWeek/ScienceDataGeneration)
 
-### Machine learning
+### 12. Machine learning
 *Yara Mohajerani and Shane Grigsby*
 
 [Machine learning](https://github.com/ICESAT-2HackWeek/Machine-Learning)