Fix heading formats and add logo in index

courses/git/github-hooks.md

@@ -1,4 +1,4 @@
-## Git with Github
+# Git with Github
 
 Till now all the operations we did were in our local repo while git also helps us in a collaborative environment. GitHub is one place on the internet where you can centrally host your git repos and collaborate with other developers.
 

courses/index.md

@@ -1,5 +1,5 @@
 # School of SRE
-
+![School of SRE](img/sos.png)
 Early 2019, we started visiting campuses to recruit the brightest minds to ensure LinkedIn and all the services that it is composed of is always available for everyone. This function at Linkedin falls in the purview of the Site Reliability Engineering team and Site Reliability Engineers ( SRE ) who are Software Engineers who specialize in reliability. SREs apply the principles of computer science and engineering to the design and development of computer systems: generally, large distributed ones.  
 
 As we continued on this journey we started getting a lot of questions from these campuses on what exactly site engineering roll entails? and, how could someone learn the skills and the disciplines involved to become a successful site engineer?   Fast forward a few months, and a few of these campus students had joined LinkedIn either as Interns or as full time engineers to become a part of the Site Engineering team, we also had a few lateral hires who joined our organization who were not from a traditional SRE background.  That's when a few of us got together and started to think about how we can on board new new graduate engineers to the site engineering team.

courses/systems_design/availability.md

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-## HA - Availability - Common “Nines”
+# HA - Availability - Common “Nines”
 Availability is generally expressed as “Nines”, common ‘Nines’  are listed below.
 
 | Availability %                  | Downtime per year |  Downtime per month | Downtime per week | Downtime per day |

courses/systems_design/conclusion.md

@@ -1,3 +1,3 @@
-## Conclusion
+# Conclusion
 
 Armed with these principles, we hope the course will give a fresh perspective to design software systems. It might be over engineering to get all this on day zero. But some are really important from day 0 like eliminating single points of failure, making scalable services by just increasing replicas. As a bottleneck is reached, we can split code by services, shard data to scale. As the organisation matures, bringing in [chaos engineering](https://en.wikipedia.org/wiki/Chaos_engineering) to measure how systems react to failure will help in designing robust software systems.

courses/systems_design/fault-tolerance.md

@@ -1,4 +1,4 @@
-## Fault Tolerance
+# Fault Tolerance
 
 Failures are not avoidable in any system and will happen all the time, hence we need to build systems that can tolerate failures or recover from them.