Dev/governance docs to snake-case (#693)

* Update GOVERNANCE.md - fix link to CODE_OF_CONDUCT.md
* Update and rename STEERING-COMMITTEE.md to STEERING_COMMITTEE.md - switch filenames to snake case following MVG example
* Update CHARTER.md - snake case all governance docs following MVG example

CHARTER.md

@@ -1,6 +1,6 @@
 # Charter for the CausalML Organization
 
-This is the organizational charter for the CausalML Organization (the "Organization"). By adding their name to the [Steering Committee.md file](./STEERING-COMMITTEE.md), Steering Committee members agree as follows.
+This is the organizational charter for the CausalML Organization (the "Organization"). By adding their name to the [Steering Committee.md file](./STEERING_COMMITTEE.md), Steering Committee members agree as follows.
 
 ## 1. Mission
 
@@ -42,7 +42,7 @@ Information disclosed in connection with any of the Organization's activities, i
 
 ## 8. Amendments
 
-Amendments to this charter, the [antitrust policy](./ANTITRUST.md), the [trademark policy](./TRADEMARKS.md), or the [code of conduct](./CODE-OF-CONDUCT.md) may only be made with at least a 3/4 affirmative vote of the Steering Committee.
+Amendments to this charter, the [antitrust policy](./ANTITRUST.md), the [trademark policy](./TRADEMARKS.md), or the [code of conduct](./CODE_OF_CONDUCT.md) may only be made with at least a 3/4 affirmative vote of the Steering Committee.
 
 ---
 Adapted from [MVG-0.1-beta](https://github.com/github/MVG/tree/v0.1-beta).

STEERING-COMMITTEE.md → STEERING_COMMITTEE.md

@@ -1,6 +1,6 @@
 # Steering Committee
 
-This document lists the members of the Organization's Steering Committee. Voting members may be added once approved by the Steering Committee as described in the [charter](./CHARTER.md). By adding your name to this list you are agreeing to abide by all Organization polices, including the [charter](./CHARTER.md), the [code of conduct](./CODE-OF-CONDUCT.md), the [trademark policy](./TRADEMARKS.md), and the [antitrust policy](./ANTITRUST.md). If you are serving on the Steering Committee because of your affiliation with another organization (designated below), you represent that you have authority to bind that organization to these policies.
+This document lists the members of the Organization's Steering Committee. Voting members may be added once approved by the Steering Committee as described in the [charter](./CHARTER.md). By adding your name to this list you are agreeing to abide by all Organization polices, including the [charter](./CHARTER.md), the [code of conduct](./CODE_OF_CONDUCT.md), the [trademark policy](./TRADEMARKS.md), and the [antitrust policy](./ANTITRUST.md). If you are serving on the Steering Committee because of your affiliation with another organization (designated below), you represent that you have authority to bind that organization to these policies.
 
 | **NAME** | **Handle** | **Affiliated Organization** |
 | --- | --- | --- |