maven: add index nginx host in docker dev setup

Adds a container to the docker-dev setup to run a nginx server to host the extracted maven index file. This "external" server is required to run the maven-lister. The served directory is in conf/maven-index, feel free to use any fld file instead.

Command used to run the lister:

swh scheduler task add  list-maven-full url=https://repo1.maven.org/maven2/ index_url=http://swh-lister-maven-nginx/export.fld

Related to T1724

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Migrated from D6955 (view on Phabricator)

docker/conf/maven_index/export.fld

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+  field 0
+    name u
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+    value al.aldi|sprova4j|0.1.0|sources|jar
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+    type string
+    value al.aldi|sprova4j|0.1.1|sources|jar
+  field 1
+    name m
+    type string
+    value 1626111784883
+  field 2
+    name i
+    type string
+    value jar|1626111425534|14510|2|2|0|jar
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+    name n
+    type string
+    value sprova4j
+  field 11
+    name d
+    type string
+    value Java client for Sprova Test Management
+doc 3
+  field 0
+    name u
+    type string
+    value al.aldi|sprova4j|0.1.1|NA|pom
+  field 1
+    name m
+    type string
+    value 1626111784915
+  field 2
+    name i
+    type string
+    value jar|1626111437014|-1|1|0|0|pom
+  field 10
+    name n
+    type string
+    value sprova4j
+  field 11
+    name d
+    type string
+    value Java client for Sprova Test Management
+doc 4
+  field 14
+    name DESCRIPTOR
+    type string
+    value NexusIndex
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+    name IDXINFO
+    type string
+    value 1.0|index
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+  field 16
+    name allGroups
+    type string
+    value allGroups
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+    name allGroupsList
+    type string
+    value al.aldi
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+    name rootGroups
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+    name rootGroupsList
+    type string
+    value al
+END
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