Method -> Call, expose findMethod on api (#1222)

* Rename Method -> Call (interface, align with Rust)

* Export Call types from types, expose findCall

packages/type-jsonrpc/src/author.ts

@@ -41,7 +41,7 @@ const submitAndWatchExtrinsic: RpcMethodOpt = {
 const section = 'author';
 
 /**
- * @summary Methods to work with authors & contributors.
+ * @summary Calls to work with authors & contributors.
  */
 export default {
   isDeprecated: false,

packages/type-jsonrpc/src/chain.ts

@@ -89,7 +89,7 @@ const subscribeRuntimeVersion: RpcMethodOpt = {
 const section = 'chain';
 
 /**
- * @summary Methods to retrieve chain data.
+ * @summary Calls to retrieve chain data.
  */
 export default {
   isDeprecated: false,

packages/type-jsonrpc/src/system.ts

@@ -54,12 +54,12 @@ const networkState: RpcMethodOpt = {
 const section = 'system';
 
 /**
- * @summary Methods to retrieve system info.
+ * @summary Calls to retrieve system info.
  */
 export default {
   isDeprecated: false,
   isHidden: false,
-  description: 'Methods to retrieve system info',
+  description: 'Calls to retrieve system info',
   section,
   methods: {
     chain: createMethod(section, 'chain', chain),