Changes to "Become a Member"

Created by: DBees

Under Become a Member at https://www.openhwgroup.org/membership/#tab-membership

Step 1. The document referred to is now the "Membership Information Form". This form is being updated by @ZahraFazli as part of completion of https://github.com/openhwgroup/openhwgroup.org/issues/491. When that new form is finalized please change the link text here accordingly.

Step 3. The text should say: For Platinum, Gold and Silver level memberships, complete and sign the Member Committer and Contributor Agreement. This agreement is not required for Supporter level memberships.

Step 4. The text should say: Email us the documents 1-3 above, as well as a full colour, vector based member logo on transparent background for our OpenHW member directory. @ZahraFazli @rickoco please check this over.