docs: add custom DocFX theme #81

Job	Run time
build (Release)	26s
build (Debug)	24s
dependency health	32s
examples:governance / RedisQueries	24s
examples:core / BillingQuotas	22s
test:governance-redis	24s
test:core	24s
examples:core / WorkflowApprovals	24s
test:governance	25s
examples:core / FeatureFlags	23s
examples:governance / RequestLifecycle	23s
examples:governance / VersionedResolution	28s
examples:core / IamRoles	21s
examples:governance / ApprovalWorkflow	21s
examples:governance / GovernedExecution	20s
examples:governance / DecisionTaxonomy	26s
examples:governance / Queries	21s
validation summary	3s
	6m 51s

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